T'rex controller fault

I have a new t'rex controller I intended to use with a wild thumper 6wd. While setting up the rc controls and testing the motor direction/reversing, I ran into a problem.  One of the motor outputs stopped working, and the fault led came on.  Both outputs were working initially, for about 20 seconds in total. But now this motor output goes straight into fault mode on power up.  Using a charged 7.2v NiMH pack btw.

The led will come on wether there are motors attached or not. So I'm fairly certain the problem is in the controller.  Checking the motor wiring anyway I can't find any problems.   14ga wire is used between the terminal block on the thumper and the controller.  And ohming the connections out didn't reveal any issues. 

I can't see any obvious problems outwardly on the controller.   Is there anything else I can try before going back to the retailer for a replacement?