Weid joint deformation in animations

Hi, I am having some weird looking deformations of my mesh when animating. I made a character with Fuse and use anims from Mixamo, and I use the blender-mixamo addon to give them a root bone and rename the bones to match the ue4 skeleton. And when it is animating the joints deform weirdly like this (happens to arms too). I am too new to this to know where to start looking for a solution. Any help or pointers would be awesome.