I'm waiting on batteries to charge...so here are my quick thoughts...
It maybe an overload protection kicking in. If any of the gimbal motors are in a bind they will overheat and then the gimbal will shut down. Make sure this is not the case, check by feeling around the gimbal for hot spots after a shut down. As well make sure the (powered off) gimbal has full three axis of movement without any binding.
You can also check to see if a power issue is related to the data cable. Removing the battery tray, you can keep the GPS hooked up and place the tray out over the side of the body. With the battery tray out of place, you can connect a battery to power up the system. This will give you access to the gimbal top board, main board and the data cable under power. Wiggle the data wires around to see if this is the source of the problem.
Just a process of elimination.