After version 2.0, the core has been incompatible with Tiny Progressions. As this is a core mod I decided to post the issue here.

https://pastebin.com/26tbeEk1

This crash is occurring with Mekanism as well.

http://openeye.openmods.info/crashes/8e56b4649bf41cccd7f5a5ed038383ac

Duplicate of #72 and mekanism/Mekanism#4414 issue is in those mods and not Bookshelf. They've both said they've fixed the issue and an update will come here.