The bug
When you selelect incompatible resource pack and then you open version of the game, where the resource pack is compatible, it unselects everything and when you look to the Resource Packs menu and click done, the game reloads everything.
How to reproduce
Go to older or newer version of Minecraft
Select some incompatible resource pack
Open the game version, in which, the resource pack is compatible
→ ❌ Resource packs are unselected and game behaves weirdly
Please don't change the category! It's only for mods and Mojang to change.