Proper grounding of camera and computer equipment
The cameraback triggers the flash when the flashsync cable connected to the cameraback. This happens intermittent with no further notice. The exposure button on the camerabody has not been triggered and the flash starts firing. Or the back itself can activate the flash when touching the back with a fingertouch. In general the back seems to activate to flash itself.
These different scenarios happen due to improper grounding of the system. The Flash equipment, the computer and external devices must be properly grounded from the circuit. This also includes the use of powercables that have internal grounding (typically a third leg). The circuit itself may also be ...