Does anyone know why the elbow twists and pinches the mesh when rotating the hand, so the palm is up? I have tried a combination of rotating the hand, the elbow/lower arm the upper arm and I'm at a loss of what the correct procedure is.

I am using iClone 8.42 with live link to UE 5.4. In the attached image I have applied a pose file and used edit motion layer to modify the pose - I have also tried to do this to an animation file as well as the UE MH iAvitar dummy and I am unable to get a favorable result. What am I doing wrong?

A bit of an update on this. What I have found is that this is an issue with the IK rig, but if I use FK Mode (not the FK button in IK Mode) to rotate the palm up then I can avoid the elbow twist that is causing the unwanted mesh distortion to the MH. This is a bit of a bummer but a workaround, nonetheless. 
Note: I am using Edit Motion Layer