Synchronization issue when switching from 1.16.5 server to 1.12.2 server on 1.12.2 client (BungeeCord)

[BoomEaro]

'/viaversion dump' Output

https://dump.viaversion.com/59e54d827bfaa76f77f64bf157cb73961c2e017300cb892965e1d12358db569c

Console Error

Technically, the error only occurs from the client side (crash), there are no errors on the server side.

Bug Description

There are two strange errors at once:

1. When switching from server 1.16.5 to server 1.12.2 using the game client 1.12.2, the loading screen does not appear, the player seems to be teleported to another location, but before connecting he teleports somewhere for a moment to zero coordinates and then connects to server.
2. If you try to use plugins that can forcibly switch the player to any server using the chest as a menu, then when switching from server 1.16.5 to server 1.12.2 using the 1.12.2 client, the chest on the connected server does not disappear. It is not possible to interact with items in the chest inventory, however, if you try to do something with the hotbar, the client 1.12.2 crashes.

Steps to Reproduce

1. Use BungeeCord, install the latest dev build ViaVersion and ViaBackward on it
2. Install the server with version 1.12.2 and 1.16.5
3. On server 1.16.5, install the plugin on the menu which is able to send any player to any server by clicking. Configure so that the plugin sends the player to the 1.12.2 server.
4. Log into the BungeeCord network using the 1.12.2 client.
5. Go to server 1.16.5, try to switch to server 1.12.2 using the menu.
6. You will see that the inventory chest has not been closed and cannot be interacted with.
7. Click on any slot in the hotbar. (Client crashes)

Expected Behavior

1. The normal loading screen is the same as if the player were to switch from the main world to another world.
2. The chest or any other inventory must be closed to sync when switching from server to server.

Additional Server Info

Used only original BungeeCord and 2 servers on paper corresponding versions. BungeeCord only has the required plugins. Testing was carried out without them, the result is the same.

Possibly the same bug exists on versions above or below 1.12.2, I haven't tested this.

Checklist

• [X] Via plugins are only running on EITHER the backend servers (e.g. Paper) OR the proxy (e.g. BungeeCord), not on both.
• [X] I have included a ViaVersion dump.
• [X] If applicable, I have included a paste (not a screenshot) of the error.
• [X] I have tried a build from https://ci.viaversion.com/ and the issue still persists.