thanks for the suggestions.
@BH67 You said you were able to export it to glTF without seeing this issue? Would you mind sharing what settings you used? I just exported it to a .glTF with the default settings and it still has the same warping behaviour.
IIUC the animation baking is happening when I export to .fbx, the export settings do the baking https://imgur.com/lsqU1Yz. The exported fbx file has a keyframe for every bone for every frame, so it seems to be doing that. I thought maybe I could try baking the animation inside of blender… in Object mode there’s the object → animation → bake animation dropdown but of course nothing in blender “just works,” the baked animation doesn’t move my rig at all. Given that the same issue is happening for multiple export types (.fbx, .glTF, .blend) I’m not sure if figuring out why my animation baking isn’t working will actually reveal anything, I imagine it will just be broken in the same way unfortunately.
If I put the entire .blend file into unity, it doesn’t seem to understand that there are multiple animation actions and just shows a single one called “scene.” I assume thats whatever action was last open, because it is the overhead slam one (just with the wrong name), and it sadly has the same warping artifacts.
I filed a bug report with blender #125159 - exporting animation to FBX warps that animation - blender - Blender Projects, maybe they will have some insight