[Al Skierkiewicz]

Mikets,
One needs to look to the real world properties of the components involved. Mostly to the resistive nature of the wiring. There is no ground nor is there anything that acts like ground on the robot and no current passing through the frame as there might be in vehicle electrical systems. The only point at which all is common is the negative lead of the PD. The chassis of the Crio is tied to this common through a #18 wire of unknown length. The camera likewise is tied through a smaller wire also of unknown length and that is tied to the metallic parts of the camera case. Should a motor lead or power lead for a motor controller also be tied to the frame, a voltage is developed across the #18 wire of the Crio between the Crio chassis and the PD and some current will flow in this path. So here is a few possibilities if the Crio is not insulated from frame.
1. The return lead of a motor or speed controller input is tied to the frame. The return to the PD has a bad crimp or loose screw. Some of the motor current will attempt to flow through the Crio.
2. One lead of a speed controller is tied to frame either due to pinched wire or motor short. In one direction the frame is connected to the negative lead of the PD and only motor noise and some motor current flows on the frame. The Crio will then have noise on the chassis. In the other commanded direction, the frame is now tied to the positive lead of the battery and is subject to the PWM output of the controller pulsing to 12 volts. That raises the chassis of the Crio several volts depending on the current flow and the resulting voltage drop across the Crio power wiring. It may be enough to interrupt Crio operation, communication or if long enough it may even cause a reboot.
There are other possibilities as well, from disrupting the PD power supplies to faults on the side cars. Each one will be slightly different. It is like a road map. There are many ways to get some place, some of them are faster than others but all eventually lead back to the same destination. It is best to close all the side roads, dirt roads, paths, trails and walkways and just leave the expressway.