Any warning messages other than the triangle?
And does it ever charge? Any problems while driving/does it charge OK if you press the "charge" button?
First thing I would try would be a different EVSE or at least that the pins are all clean and the button on the handle springs up into place
I'm sure this is way to late for the OP but for future reference you can get aftermarket 360° /birdseye cameras that just have a 'RCA' video output. I fit one in my car and just ran the signal to a clip over rear view mirror screen.
Doubles as a 360° dash cam / crash recorder as well.
There...
That feature can be disabled, (can't remember how, through the head unit perhaps?) possibly it has been disabled and that's the cause of the battery drain