I don’t really wanna necro this, but I have a similar situation.
EXPORT animation from UE4, import into Modo, arms are twisted up in a horrible way.
Looks like its something to to with the bones upperarm_twist_01_ and lowerarm_twist_01_ (l and r)
An example can be seen here:
https://www.youtube.com/watch?v=XHId9h80c94
Any Modo experts shed light on this, offer some correction?