Adventure Tools' CurseForge page: https://www.curseforge.com/minecraft/mc-mods/adventure-tools

Crash report: https://paste.ubuntu.com/p/Ztjkzc6MDx/

Placing blocks won't cause crashes but items. The Mining Helmet provided by Adventure Tools actually works by automatically placing light sources on surface honoring where the players are looking at, and when placing items over those light sources, a crash would happen. The crash has been fowarded to Adventure Tools' side too: syntacticsplenda/adventurepack#20

Haven't looked extensively into it but I think this is probably due to some weird interaction with the RayTrace method. A possibility is the RayTrace returns coordinates currently occupied by a BlockLight, which Plonk freaks out when it tries to use. This might be generalized to placing any tile entity on top of a light block.

The Plonk mod is way more complex than my mod, so I would appreciate the author's insight here.

Very strange, for some reason Block#getCollisionShape (overriden in BlockPlacedItems#getCollisionShape) is being called on a position that doesn't have a TilePlacedItems which it expects, but there is a BlockPlacedItems at that location with tile TileEntityLight afaict? :(

This does seem like a bad assumption on my end though so I will add a check to make sure that it is a TilePlacedItems there.

Fixed in Plonk v9.0.8 (mc 1.16.5).

Let me know if it didn't fix it and we can re-open.

If it is fixed you can probably close syntacticsplenda/adventurepack#20 as well I think.