Loss of DS control authority while motors still operate

[MikeE]

We've been seeing some odd and somewhat alarming behavior during testing of our practice robot over the weekend. Our control system setup is Java, Jaguar CAN running closed-loop speed control of the drive motors.

Basic symptoms are a loss of control and SmartDashboard output while the driver station stays in teleop enabled state. Note that in some cases the drive motors would continue to operate at set speed although there was no control authority from the DS !
Pressing disable on the DS did stop the motors. A cRIO reboot was needed to run properly again.

Initially the onset of the problem appeared to coincide with sudden polarity reversal of one or more CIMs, implying momentary voltage drop/brownout. We implemented setpoint rate limiting and while the problem frequency decreased it was not eliminated.

The DS log viewer shows the cRIO CPU dropping off during the loss of control event, the DS staying in teleop but the robot state leaving teleop and apparently continuing to report voltage (see attached image).

Finally there was no evidence of a user code crash on the output terminal of Netbeans.

We are competing in a Week 1 regional so I'd appreciate anyone's thoughts on potential causes.