1.16.5

Closing due to no reply and no one else reporting similar.

modlist?

Does this happen with just clumps installed?
Do you have any other mods that mess with experience?

What mod does multithreaded optimizations?

You're going to need to uninstall optimization mods until it starts working, nothing in that list has known issues as far as I can tell.

modlist.txt
I suspect it's caused by multithreaded optimizations