I created an animation in blender using an armature and exported it into .fbx. I then imported this into unreal. When I playback the animations in unreal the mesh deforms incorrectly inwards, which I believe is the result from transform calculations not being done correctly when both a bone and one of its parent bones have rotations in given frames. I verified that if I rotate only the leaf bones and add scaling through the hierarchy the animation seems to work as intended. I thought it might be due to some configuration error in either the export from blender or the import to unreal but I cannot seem to figure out what is wrong. I add here a screenshot of the export settings to create the .fbx. As for the unreal import, I will simply add the .fbx here so that you can try for yourselves.
Link to the .fbx. You will find an animation called Slime2_Skeleton_Forward which is the culprit.
I think the issue might be the same or similar to this other question based on the description, but since the added download link for the .fbx is broken I couldn´t verify it