Three drive Victors work, four does not

[dman14]

My team and I came across the weirdest issue I have ever seen this week.

We have four drive motors, paired in twos into the KoP gearboxes, each controlled by a Victor 888. Everything worked fine until this week. We re-did our electronics board, but everything seems to be connected properly.

The issue is that our drive motors stopped responding to joystick input. As soon as the robot is enabled, the wheels slowly spin for 2 seconds, then jerk suddenly to what seems to be full power and immediately stop. To me this seemed like a programming issue, but the only "fix" we have found, is to disconnect one of the Victor 888s, but it does not matter which one we disconnect. Any combination of 3 Victors works fine, but as soon as the 4th pwm is plugged in, the above symptom re-occurs.

My thoughts are on a calibration issue, but not sure how it would appear with 4, and not with 3. We do not have access to the robot until Tuesday, but I can answer with any details I recall until then. I have a rather large list of items we will test when we get to work on it again, but I thought I see if anyone else has experienced this, or has input as to what to test.