I've been trying for hours to solve this and I can't do it for the life of me. I'm just trying to rig a hand right and I can't do it. I'm using Blender.
I have this hand here with little box bones for controlling the fingers. When I animate the mesh, the keyframes are fine, but inbetween the keyframes the fingers move all weird. When I export the animaton or move along the frames in the blender editor, the fingers are pointing in random directions like the keyframes don't exist at al (as seen in the attached image)l. This is how the animation looks as an fbx too, but in the editor if I try to move them back into place, just even clicking on an axis instantly snaps all of the fingers to the right place.
It's just the fingers! I've tried moving the parents around a bunch for a lot of the bones, setting and removing constraints. I'm beat.