Mixamo Retarget Issues

Hello, Everyone! I am new to UE4, and today I encountered one problem that confuse me a lot, I don’ t know how to solve this, I hope you can help me with it, thanks a lot !
This is my problem: I just download character “derrick” form Mixamo, and I did skeleton retarget with default mannequin skeleton, then I retarget an rifle aiming animation asset with this Mixamo skeleton, every other body works well except the left hand, it just twisted, and I double check my mapping, every name maps well, so now I am confused, looking forward your generous help.
:grinning: