Back up Cam in OEM Tuner- Input dead?

[IFLYTBM]

Anyone have any ideas...I got the truck back from a local shop, searching for a rampant battery draw. The shop was baffled by the updates and additions so common to this community. They couldn't properly reconnect the wiring as I had done when it was brought it in. So I left with the most rudimentary NAV screen ever. A few swapped modular plug hookups and it was almost 100%-but...the back up camera is not functioning.

The A/V input on the OEM tuner module works as evidenced by the headrest communicating with the NAV screen-everything functions including audio, but no the camera. I even tried a portable DVD player as an input and the screen wont display or play audio??

When placed in Reverse, the relay fires, the input switches to a blank screen. So I've tested the camera on another and seperate display-nothing. and I;ve swapped the A/V (Headrest input) to the CAM input while in Reverse-nothing...its as if both the camera and the input have been killed and I'm not getting anywhere.

Nothing changed in the pinouts, they didn't know what they were doing so they disconnected everything and in their defense this did happen once before following a series of flat batteries (darn FSR), but it eventually came back to life on its own 3 days later-same symptoms then as now, but I'm X? days into this and hours of troubleshooting in and out of the truck. Has anyone ever heard of just this input dying???