Tunnel Tube biome spawns unexpected nodes from other mods

[BramvdnHeuvel]

I am hosting a Minetest 5.8.0 server using Docker with the dfcaverns mod, the tpad mod and a few others. On our server, the tpad is meant to be rare and difficult to obtain. However, the tpad seems to spawn abundantly in the tunnel tube biome:

How to replicate

1. Start a MineClone2 game (singleplayer or server) and load the dfcaverns modpack + the tpad mod
2. Find a tunnel tube biome
3. Look around, there's a few tpads spawning here and there. If you cannot find them, you can consider trying the seed and coordinates from the screenshots.

[BramvdnHeuvel]

I made this bug report here because the modpack doesn't seem to have the tpad as a dependency. The node is registered as tpad:tpad so I would be surprised if this mod intended to access it.

I couldn't find any references in the modpack either, and the tpad mod offers no support to naturally generate the node.

[BramvdnHeuvel]

I am suspecting the bug is unrelated to the tpad mod; with the tpad mod deactivated, an unrelated node of a different mod can appear:

I am suspecting that the bug is related to the file df_caverns/node_ids.lua: the content ID is cached - but maybe it changes with the addition of other mods?