After updating to version 2.3.1 of First-person Model and trying to hit a mob my game crashed.
Version 2.3.0 worked fine.
Details:
• Fabric Loader — 0.15.6
• Fabric — 1.20.1
• Fabric API — 0.91.0+1.20.1
• First-person Model — 2.3.1-1.20.1 - Fabric
• Better Combat — 1.8.3+1.20.1
• playerAnimator — 1.0.2-rc1+1.20-fabric

Crash report and latest.log:
https://gist.github.com/mpustovoi/b7bc2ed04ebfe1b93f3fe725946bf384

Better Combat will have to update, it's not using the API but instead calling into internals. For the dev version I re-added the field its trying to get as a workaround against the crash.