Really low res from imgur prevents any checking.
Also, the UE4 skeleton seems to be missing bones entirely as if they are out of the screen?
Best curse of action is to test an import without selecting an existing skeleton.
If you still see the problem, than the animation is wrong.
could be a bone turned over 360 or similar - or something happening during the animation.
If you don’t see the problem anymore, then the issue is exactly that the 2 skeletons do not match.
If you share the FBX we can load it in and test too. You can probably delete the mesh and mats off it for file size issue. Or export just the animation.