Forearm not rotating in live characters

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Hi, I am doing some research on live characters. Now I have a problem on the forearm not rotating. I use the motion capture(blade) to get the real time data and stream the data into motionbuilder. The skeleton from motion capture is good and moving with subject, and other bones is right. Only the forearm is not
rotating with the real-time human motion.
Does anyone know what's the problem and how to fix it? Thanks.

Qiufeng