Thanks for reply, GG!
1. I and my team members had tested recording track on more than three hosts, and this problem always raised. Maybe something wrong, we don't know. I'll test again to confirm this night :-)
2. Meybe you misunderstand the question. I mean that while playing back or editing an MP track (not while recording track in MP mode), when I paused, the camera cannot be controlled. You know, you cannot pause in MP mode. However, while playing or editing a single-player track, I can control the camera when I paused a track. And this problem has been confirmed by many of my team members.