Blender exported to UE4 Gun Animation Skeletal Mesh is Twisted The Summary

I imported this Blender animation to UE4 and the the skeletal mesh is all twisted up. It is just a pistol reload animation that I have been working on. The mesh is comprised of multiple parts that are joined together. At least, I believe so. The armature consists of the trigger bone, the slide bone, the barrel bone, the magazine bone, and finally, the frame bone, which is the root. I made a parent to the hand so that the mesh would move with the hand, rather than having to select all of the bones in order to move the model. I exported the model while the mesh is parented to the right hand. The animation looks fine in Blender but in Unreal Engine 4 the mesh's movement and and the mesh itself is twisted and contorted. I have all of the mesh parts joined together. It might have to do something with the bones, not the mesh parts themselves. I assigned each vertex group to a bone and the vertex groups are weight painted.

In Blender, It looks fine.



In Unreal Engine, in the animation viewport, the mesh is twisted up.
The model I was using did not have a frame bone attached I reimported a model with the frame bone attached which is also the root bone. This solved my problem, I guess this is what happens when you import to unreal engine 4 without a root bone attached to the skeleton.