PaperMC
"java.lang.IllegalStateException: Already sent chunk [x, y] to player ..." - Double sending chunk to a player
Stack trace
[13:50:12 ERROR]: [io.papermc.paper.threadedregions.TickRegionScheduler] Region #19793 centered at chunk [-25, 2] in world 'world' failed to tick:
java.lang.IllegalStateException: Already sent chunk [8, 0] to player EntityPlayer['BEBRA_B_POPE'/2383115, uuid='10d4f404-b483-3340-91f5-fe6f1d600cb7', l='ServerLevel[world]', x=-2.06, y=71.00, z=9.72, cpos=[-1, 0], tl=71871, v=true](BEBRA_B_POPE at -2.06269412992101,71.00133597911214,9.717645408324085)
at net.minecraft.server.level.ChunkHolder.addPlayer(ChunkHolder.java:136) ~[?:?]
at net.minecraft.server.level.ChunkMap.updateChunkTracking(ChunkMap.java:733) ~[folia-1.19.4.jar:git-Folia-"d34fb87"]
at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader$PlayerChunkLoaderData.sendChunk(RegionizedPlayerChunkLoader.java:491) ~[folia-1.19.4.jar:git-Folia-"d34fb87"]
at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader$PlayerChunkLoaderData.midTickUpdate(RegionizedPlayerChunkLoader.java:885) ~[folia-1.19.4.jar:git-Folia-"d34fb87"]
at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader.tickMidTick(RegionizedPlayerChunkLoader.java:247) ~[folia-1.19.4.jar:git-Folia-"d34fb87"]
at io.papermc.paper.threadedregions.RegionizedTaskQueue$RegionTaskQueueData.drainTasks(RegionizedTaskQueue.java:232) ~[folia-1.19.4.jar:git-Folia-"d34fb87"]
at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1523) ~[folia-1.19.4.jar:git-Folia-"d34fb87"]
at io.papermc.paper.threadedregions.TickRegions$ConcreteRegionTickHandle.tickRegion(TickRegions.java:316) ~[folia-1.19.4.jar:git-Folia-"d34fb87"]
at io.papermc.paper.threadedregions.TickRegionScheduler$RegionScheduleHandle.runTick(TickRegionScheduler.java:385) ~[folia-1.19.4.jar:git-Folia-"d34fb87"]
at ca.spottedleaf.concurrentutil.scheduler.SchedulerThreadPool$TickThreadRunner.run(SchedulerThreadPool.java:525) ~[folia-1.19.4.jar:git-Folia-"d34fb87"]
at java.lang.Thread.run(Thread.java:833) ~[?:?]
Plugin and Datapack List
no plugins
Actions to reproduce (if known)
No response
Folia version
version [16:13:15 INFO]: This server is running Folia version git-Folia-"d34fb87" (MC: 1.19.4) (Implementing API version 1.19.4-R0.1-SNAPSHOT) (Git: d34fb87) You are 7 version(s) behind Download the new version at: https://papermc.io/downloads Previous version: git-Paper-499 (MC: 1.19.4)
Other
No response
please try on latest, with a bit of luck 25e0cbdae46912d227a31703869594538b731931 fixed this
Thank you, I updated the server and will close the task. If the error reoccurs, I will let you know.
Can reproduce on 41c5548.
Context: A player going to the nether, 32 chunks view distance.
[14:31:28] [Region Scheduler Thread #5/ERROR]: [io.papermc.paper.threadedregions.TickRegionScheduler] Region #29483 centered at chunk [3, 30] in world 'world_nether' failed to tick:
net.minecraft.ReportedException: Exception ticking world
at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1716) ~[folia-1.19.4.jar:git-Folia-"41c5548"]
at net.minecraft.server.dedicated.DedicatedServer.tickChildren(DedicatedServer.java:456) ~[folia-1.19.4.jar:git-Folia-"41c5548"]
at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1542) ~[folia-1.19.4.jar:git-Folia-"41c5548"]
at io.papermc.paper.threadedregions.TickRegions$ConcreteRegionTickHandle.tickRegion(TickRegions.java:360) ~[folia-1.19.4.jar:git-Folia-"41c5548"]
at io.papermc.paper.threadedregions.TickRegionScheduler$RegionScheduleHandle.runTick(TickRegionScheduler.java:385) ~[folia-1.19.4.jar:git-Folia-"41c5548"]
at ca.spottedleaf.concurrentutil.scheduler.SchedulerThreadPool$TickThreadRunner.run(SchedulerThreadPool.java:525) ~[folia-1.19.4.jar:git-Folia-"41c5548"]
at java.lang.Thread.run(Thread.java:833) ~[?:?]
Caused by: java.lang.IllegalStateException: Already sent chunk [70, 58] to player EntityPlayer['PLAYER'/1792156, uuid='UUID', l='ServerLevel[world_nether]', x=1123.50, y=131.00, z=830.03, cpos=[70, 51], tl=7943715, v=true](PLAYER at 1123.5,131.0,830.0286462521499)
at net.minecraft.server.level.ChunkHolder.addPlayer(ChunkHolder.java:136) ~[?:?]
at net.minecraft.server.level.ChunkTracker.updateChunkTracking(ChunkTracker.java:733) ~[?:?]
at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader$PlayerChunkLoaderData.sendChunk(RegionizedPlayerChunkLoader.java:485) ~[folia-1.19.4.jar:git-Folia-"41c5548"]
at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader$PlayerChunkLoaderData.updateQueues(RegionizedPlayerChunkLoader.java:860) ~[folia-1.19.4.jar:git-Folia-"41c5548"]
at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader.tick(RegionizedPlayerChunkLoader.java:244) ~[folia-1.19.4.jar:git-Folia-"41c5548"]
at net.minecraft.server.level.ServerChunkCache.tick(ServerChunkCache.java:598) ~[?:?]
at net.minecraft.server.level.ServerLevel.tick(ServerLevel.java:738) ~[?:?]
at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1697) ~[folia-1.19.4.jar:git-Folia-"41c5548"]
... 6 more
kugge put it in https://github.com/PaperMC/Folia/issues/46 (most recent open issue on it)
kugge put it in #46 (most recent open issue on it)
Unfortunately my stacktrace is not the same as yours:
Caused by: java.lang.IllegalStateException: Illegal recursive processTicketUpdates!
Whereas mine is
Caused by: java.lang.IllegalStateException: Already sent chunk [70, 58] to player EntityPlayer<...> which is exactly the same as the author
It is something related with the player connection, and mainly when respawn, I got it as well with a player known to have some ping issues. It is important to mention that it stops the server right after (got it twice with same player). The server was with very low usage, 4 players.
[21:39:16 INFO]: Checking version, please wait... [21:39:17 INFO]: This server is running Folia version git-Folia-26 (MC: 1.19.4) (Implementing API version 1.19.4-R0.1-SNAPSHOT) (Git: 25e0cbd) You are running the latest version
Adding my Stack trace
[23:07:40] [Region Scheduler Thread #0/INFO]: Cogumelo090 fell from a high place [23:07:42] [Region Scheduler Thread #0/ERROR]: [io.papermc.paper.threadedregions.TickRegionScheduler] Region #714 centered at chunk [-178, 183] in world 'world' failed to tick: net.minecraft.ReportedException: Exception ticking world at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1716) ~[folia-1.19.4.jar:git-Folia-26] at net.minecraft.server.dedicated.DedicatedServer.tickChildren(DedicatedServer.java:447) ~[folia-1.19.4.jar:git-Folia-26] at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1542) ~[folia-1.19.4.jar:git-Folia-26] at io.papermc.paper.threadedregions.TickRegions$ConcreteRegionTickHandle.tickRegion(TickRegions.java:360) ~[folia-1.19.4.jar:git-Folia-26] at io.papermc.paper.threadedregions.TickRegionScheduler$RegionScheduleHandle.runTick(TickRegionScheduler.java:385) ~[folia-1.19.4.jar:git-Folia-26] at ca.spottedleaf.concurrentutil.scheduler.SchedulerThreadPool$TickThreadRunner.run(SchedulerThreadPool.java:525) ~[folia-1.19.4.jar:git-Folia-26] at java.lang.Thread.run(Thread.java:833) ~[?:?] Caused by: java.lang.IllegalStateException: Already sent chunk [-178, 180] to player EntityPlayer['Cogumelo090'/49553, uuid='fd6045ea-5125-3cd7-a337-37b75f051545', l='ServerLevel[world]', x=-2843.50, y=108.00, z=2930.50, cpos=[-178, 183], tl=81841, v=true](Cogumelo090 at -2843.5,108.0,2930.5) at net.minecraft.server.level.ChunkHolder.addPlayer(ChunkHolder.java:136) ~[?:?] at net.minecraft.server.level.ChunkTracker.updateChunkTracking(ChunkTracker.java:733) ~[?:?] at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader$PlayerChunkLoaderData.sendChunk(RegionizedPlayerChunkLoader.java:485) ~[folia-1.19.4.jar:git-Folia-26] at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader$PlayerChunkLoaderData.updateQueues(RegionizedPlayerChunkLoader.java:860) ~[folia-1.19.4.jar:git-Folia-26] at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader.tick(RegionizedPlayerChunkLoader.java:244) ~[folia-1.19.4.jar:git-Folia-26] at net.minecraft.server.level.ServerChunkCache.tick(ServerChunkCache.java:598) ~[?:?] at net.minecraft.server.level.ServerLevel.tick(ServerLevel.java:739) ~[?:?] at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1697) ~[folia-1.19.4.jar:git-Folia-26] ... 6 more [23:07:42] [Region shutdown thread/INFO]: [RegionShutdownThread] Awaiting scheduler termination for 60s [23:07:42] [Region shutdown thread/INFO]: [RegionShutdownThread] Scheduler halted [23:07:42] [Region shutdown thread/INFO]: Stopping server
Please try again on latest, I have made some changes to provide more debugging information
New stacktrace world_nether => world
[02:28:47] [Region Scheduler Thread #2/ERROR]: [io.papermc.paper.threadedregions.TickRegionScheduler] Region #78955 centered at chunk [24, -3] in world 'world' failed to tick:
net.minecraft.ReportedException: Exception ticking world
at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1716)
at net.minecraft.server.dedicated.DedicatedServer.tickChildren(DedicatedServer.java:456)
at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1542)
at io.papermc.paper.threadedregions.TickRegions$ConcreteRegionTickHandle.tickRegion(TickRegions.java:360)
at io.papermc.paper.threadedregions.TickRegionScheduler$RegionScheduleHandle.runTick(TickRegionScheduler.java:385)
at ca.spottedleaf.concurrentutil.scheduler.SchedulerThreadPool$TickThreadRunner.run(SchedulerThreadPool.java:525)
at java.lang.Thread.run(Thread.java:833)
Caused by: java.lang.IllegalStateException: Already sent chunk [-11, 4] in world 'world' to player EntityPlayer['player'/4341049, uuid='uuid', l='ServerLevel[world]', x=-9.50, y=68.00, z=67.89, cpos=[-1, 4], tl=22713701, v=true]
at net.minecraft.server.level.ChunkHolder.addPlayer(ChunkHolder.java:136)
at net.minecraft.server.level.ChunkTracker.updateChunkTracking(ChunkTracker.java:735)
at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader$PlayerChunkLoaderData.sendChunk(RegionizedPlayerChunkLoader.java:485)
at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader$PlayerChunkLoaderData.updateQueues(RegionizedPlayerChunkLoader.java:860)
at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader.tick(RegionizedPlayerChunkLoader.java:244)
at net.minecraft.server.level.ServerChunkCache.tick(ServerChunkCache.java:598)
at net.minecraft.server.level.ServerLevel.tick(ServerLevel.java:738)
at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1697)
It seems that when a player sleep when this crash occur, the player cannot connect anymore and we have to delete his player.dat + restart. We cannot sleep on his bed (the bed is bugged).
Edit: Not related to this issue but to #57
New stacktrace world_nether => world
Are there any other logs? Some of the debugging information wont cause a crash, but rather log some warnings/errors.
New stacktrace world_nether => world
Are there any other logs? Some of the debugging information wont cause a crash, but rather log some warnings/errors.
I don't have any more details, but I've already encountered those:
[14:28:39] [Region Scheduler Thread #4/WARN]: Boat (vehicle of Byron_11) moved wrongly! 0.691516229135047
[14:28:39] [Region Scheduler Thread #0/WARN]: Boat (vehicle of Byron_11) moved wrongly! 2.6681221076020734
[14:28:39] [Region Scheduler Thread #1/WARN]: Boat (vehicle of Byron_11) moved wrongly! 4.645049069264047
[14:28:39] [Region Scheduler Thread #2/WARN]: Boat (vehicle of Byron_11) moved wrongly! 6.622283044442213
[14:28:39] [Region Scheduler Thread #3/WARN]: Boat (vehicle of Byron_11) moved wrongly! 8.599866519086376
[14:28:39] [Region Scheduler Thread #4/WARN]: Boat (vehicle of Byron_11) moved wrongly! 10.57786562693714
[14:28:39] [Region Scheduler Thread #5/WARN]: Boat (vehicle of Byron_11) moved wrongly! 12.556303265820418
[14:28:39] [Region Scheduler Thread #0/WARN]: Boat (vehicle of Byron_11) moved wrongly! 14.521254581748849
[14:28:39] [Region Scheduler Thread #1/WARN]: Boat (vehicle of Byron_11) moved wrongly! 16.474170132178003
[14:28:39] [Region Scheduler Thread #2/WARN]: Boat (vehicle of Byron_11) moved wrongly! 18.416303841197376
[14:28:39] [Region Scheduler Thread #3/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.01578716118792478,0.0,-21.758311789394057
[14:28:39] [Region Scheduler Thread #5/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.031750630766437915,0.0,-23.73798891655072
[14:28:39] [Region Scheduler Thread #0/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.05341953557262791,0.0,-25.717616219770278
[14:28:39] [Region Scheduler Thread #2/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.08039906871508151,0.0,-27.697236444858902
[14:28:39] [Region Scheduler Thread #3/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.11161742760527815,0.0,-29.67697786101361
[14:28:39] [Region Scheduler Thread #1/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.1460443168516612,0.0,-31.656940422843363
[14:28:39] [Region Scheduler Thread #4/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.1826831795304784,0.0,-33.637198471251665
[14:28:39] [Region Scheduler Thread #0/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.22057495434837193,0.0,-35.61780208017518
[14:28:39] [Region Scheduler Thread #3/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.2587940527137107,0.0,-37.598778931455925
[14:28:39] [Region Scheduler Thread #4/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.2964558563273396,0.0,-39.580135746159314
[14:28:46] [Region Scheduler Thread #0/WARN]: Byron_11 moved wrongly!
Just before a crash. That player triggered the crash
New stacktrace world_nether => world
Are there any other logs? Some of the debugging information wont cause a crash, but rather log some warnings/errors.
Had similar error, and still crashed the server, without anything related to it, not command executed etc
New stacktrace world_nether => world
Are there any other logs? Some of the debugging information wont cause a crash, but rather log some warnings/errors.
I don't have any more details, but I've already encountered those:
[14:28:39] [Region Scheduler Thread #4/WARN]: Boat (vehicle of Byron_11) moved wrongly! 0.691516229135047 [14:28:39] [Region Scheduler Thread #0/WARN]: Boat (vehicle of Byron_11) moved wrongly! 2.6681221076020734 [14:28:39] [Region Scheduler Thread #1/WARN]: Boat (vehicle of Byron_11) moved wrongly! 4.645049069264047 [14:28:39] [Region Scheduler Thread #2/WARN]: Boat (vehicle of Byron_11) moved wrongly! 6.622283044442213 [14:28:39] [Region Scheduler Thread #3/WARN]: Boat (vehicle of Byron_11) moved wrongly! 8.599866519086376 [14:28:39] [Region Scheduler Thread #4/WARN]: Boat (vehicle of Byron_11) moved wrongly! 10.57786562693714 [14:28:39] [Region Scheduler Thread #5/WARN]: Boat (vehicle of Byron_11) moved wrongly! 12.556303265820418 [14:28:39] [Region Scheduler Thread #0/WARN]: Boat (vehicle of Byron_11) moved wrongly! 14.521254581748849 [14:28:39] [Region Scheduler Thread #1/WARN]: Boat (vehicle of Byron_11) moved wrongly! 16.474170132178003 [14:28:39] [Region Scheduler Thread #2/WARN]: Boat (vehicle of Byron_11) moved wrongly! 18.416303841197376 [14:28:39] [Region Scheduler Thread #3/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.01578716118792478,0.0,-21.758311789394057 [14:28:39] [Region Scheduler Thread #5/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.031750630766437915,0.0,-23.73798891655072 [14:28:39] [Region Scheduler Thread #0/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.05341953557262791,0.0,-25.717616219770278 [14:28:39] [Region Scheduler Thread #2/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.08039906871508151,0.0,-27.697236444858902 [14:28:39] [Region Scheduler Thread #3/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.11161742760527815,0.0,-29.67697786101361 [14:28:39] [Region Scheduler Thread #1/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.1460443168516612,0.0,-31.656940422843363 [14:28:39] [Region Scheduler Thread #4/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.1826831795304784,0.0,-33.637198471251665 [14:28:39] [Region Scheduler Thread #0/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.22057495434837193,0.0,-35.61780208017518 [14:28:39] [Region Scheduler Thread #3/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.2587940527137107,0.0,-37.598778931455925 [14:28:39] [Region Scheduler Thread #4/WARN]: Boat (vehicle of Byron_11) moved too quickly! 0.2964558563273396,0.0,-39.580135746159314 [14:28:46] [Region Scheduler Thread #0/WARN]: Byron_11 moved wrongly!Just before a crash. That player triggered the crash
But it looks like we're having similar problems https://paste.ubuntu.com/p/TrN33srzR4/
On latest master. Sometimes happens
[12:36:44] [Region Scheduler Thread #4/INFO]: alan_banan228 tried to swim in lava
[12:36:47] [Region Scheduler Thread #4/ERROR]: [io.papermc.paper.threadedregions.TickRegionScheduler] Region #5637 centered at chunk [-12, -27] in world 'world' failed to tick:
net.minecraft.ReportedException: Exception ticking world
at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1698) ~[folia-1.19.4.jar:git-Folia-"ca3b7ad"]
at net.minecraft.server.dedicated.DedicatedServer.tickChildren(DedicatedServer.java:447) ~[folia-1.19.4.jar:git-Folia-"ca3b7ad"]
at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1536) ~[folia-1.19.4.jar:git-Folia-"ca3b7ad"]
at io.papermc.paper.threadedregions.TickRegions$ConcreteRegionTickHandle.tickRegion(TickRegions.java:360) ~[folia-1.19.4.jar:git-Folia-"ca3b7ad"]
at io.papermc.paper.threadedregions.TickRegionScheduler$RegionScheduleHandle.runTick(TickRegionScheduler.java:385) ~[folia-1.19.4.jar:git-Folia-"ca3b7ad"]
at ca.spottedleaf.concurrentutil.scheduler.SchedulerThreadPool$TickThreadRunner.run(SchedulerThreadPool.java:525) ~[folia-1.19.4.jar:git-Folia-"ca3b7ad"]
at java.lang.Thread.run(Thread.java:1589) ~[?:?]
Caused by: java.lang.IllegalStateException: Already sent chunk [-3, 5] in world 'world' to player EntityPlayer['alan_banan228'/239391, uuid='b1b6619b-8211-3e47-94f1-c474684ee23c', l='ServerLevel[world]', x=-32.50, y=240.00, z=-13.50, cpos=[-3, -1], tl=256384, v=true](alan_banan228 at -32.5,240.0000002,-13.5)
at net.minecraft.server.level.ChunkHolder.addPlayer(ChunkHolder.java:136) ~[?:?]
at net.minecraft.server.level.ChunkTracker.updateChunkTracking(ChunkTracker.java:735) ~[?:?]
at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader$PlayerChunkLoaderData.sendChunk(RegionizedPlayerChunkLoader.java:485) ~[folia-1.19.4.jar:git-Folia-"ca3b7ad"]
at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader$PlayerChunkLoaderData.updateQueues(RegionizedPlayerChunkLoader.java:860) ~[folia-1.19.4.jar:git-Folia-"ca3b7ad"]
at io.papermc.paper.chunk.system.RegionizedPlayerChunkLoader.tick(RegionizedPlayerChunkLoader.java:244) ~[folia-1.19.4.jar:git-Folia-"ca3b7ad"]
at net.minecraft.server.level.ServerChunkCache.tick(ServerChunkCache.java:598) ~[?:?]
at net.minecraft.server.level.ServerLevel.tick(ServerLevel.java:739) ~[?:?]
at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1679) ~[folia-1.19.4.jar:git-Folia-"ca3b7ad"]
... 6 more
[12:36:47] [Region shutdown thread/INFO]: [RegionShutdownThread] Awaiting scheduler termination for 60s
[12:36:47] [Region shutdown thread/INFO]: [RegionShutdownThread] Scheduler halted
[12:36:47] [Region shutdown thread/INFO]: Stopping server
As I understood, player teleported (after dying) to new region, wich have neibor region closely. And some chunks sends from neighbor, some from new region. Maybe...
It happend not only on spawn, when I used Paperlib.asyncTeleport instead of player.asyncTeleport. But with player.asyncTeleport it happens only on spawn when player respawns.
From stacktrace above:
Region #5637 centered at chunk [-12, -27] -192, 100, -432
Already sent chunk [-3, 5] -48 , 100, 80
Current player position (Spawn center [-3,1]) -32.5,240.0000002,-13.5
paper-world-defaults.yml spawn: keep-spawn-loaded: true keep-spawn-loaded-range: 10
server.properties simulation-distance=7 view-distance=8
Can you add full debug info with that error message? In the same place in code, what you need to know? (Or maybe I can add in my local version.)
Player positions, players in regions, region positions, region sizes, latest switches players between regions, regions by threads, chunk loads by threads/regions/players ...
What we can add easily(or not) to debug this case?
Who knows how to simulate low speed chunks loading for local players?