[When I stand still for a second of more my avatars legs bend forward]

I experience this same issue (my avatar appears half crouched when standing and walking in every sim) after I updated to Firestorm version Firestorm 6.5.6 (66221) Jul 16 2022. I am not sure if this is related to the update.

I managed to fix this issue by checking on the parameter Preferences -> Firestorm -> Extras : Fix Bento Idle Animation.

[What is happening to right hands?]

Caitlin, I experienced the same issue as you describe, on me and it was random. When I detected it, I took everything off and there was no issue with any attachment in my case. I logged off and also I deleted some of the files that SL maintains between sessions in the PC (maybe this list is not comprehensive, but these are the files that I delete from the Temp directory I defined in SL:

del *.dsf
del avatar_*.*
del *.inv.gz
del data.db2.x*
del index.db2.x*
del name.cache
del *.cached_mute
del experience_cache.*
del texture_list*.*
rmdir texturecache /S /Q
rmdir objectcache /S /Q
rmdir cef_cache /S /Q

Then I logged back to SL and the movement of my hand was gone. 

Maybe you can expand and fit this workaround for your specific case.