Interesting Talon SRX Failure

[Oblarg]

Over the past two meetings we spent about four hours trying to diagnose a perplexing problem - our test base drive (6 CIM tank) would work fine in open-loop control, but half of it would not move in closed-loop control mode (even with a pure F loop, which is basically open-loop control).

As it turns out, the Talon SRX that was being used as the master for that side of the drive does not function in speed control mode, yet functions fine in percent vbus mode. We set it to be a slave and picked another talon as master, and the drive is now working. We'd send it back, but we're currently short on Talons.

Has anyone else had this failure mode? Any idea what could cause it, or if it's fixable?