Make sure that you did never run FNIS on your mod set, because FNIS modifies .hkx files in each mod directory DIRECTLY, despite you may think that changes happening only in MO2 overwrite directory. Sometimes FNIS breaks .hkx behavior files, so Nemesis can not process them correctly. Thus if you ever decide to change animations patcher from FNIS to Nemesis or vice versa, make sure that you did backup of all you animation mods. Otherwise, you need to try to reinstall all animation mods, since they may have .hkx behavior files modified by FNIS previously. After reinstalling animations the problem will go away.
I used XPMSE + Nemesis from the start without issues. Also, if you're using ModOrganizer2 delete all Nemesis generated files out of overwrite before running it again.
Yeah I think I found the problem, I narrowed down my animations mods as you said and it seems that Ultimate Combat is the culprit even though I patched it in Nemesis it's still missing up the skeleton arm fix, do you happen to know why that is?