I don’t know if this would solve the problem, but here are a few options:
- the weights of your skeletal mesh are off, so you would need to go back and repaint/blend those weights
- the proportions of your target skeletal mesh is very different than your source skeleton.
you might want to try working backward, export the source skeleton out into a 3d package, then try skinning your mesh to those exact bones. Then re-import that target skeletal mesh and try retargeting. If that doesn’t work, i would recommend using IKinema () or Motionbuilder for your retargeting.
in my honest opinion though, i honestly think it’s a skinning weights issue.
hope this helps