We also seem to recall also having issues getting a Kinect 2 working on an older MacMini using thunderbolt. We never really discovered the reason why it didn't work - it simply appeared like the USB device was lost randomly. Curously enough we did get thunderbolt working on a newer MacBook Pro though.
The libfreenect2 people seemed to say this could be a kernel problem. If this is the case I'm afraid there's nothing we can do about this problem. The troubleshooting page there says this: