I built a Retropie using a PI Model 3B that is powered via the GPIO pins. Specifically with this case which adapts micro usb to the GPIO power. Everything works fine except when I turn the system off. Once the GPIO power is cut, the system tries to power itself over HDMI. The power coming from HDMI is not enough for the system to boot, so it just starts a never ending loop of boot up then crash.
Is there any way to disable power over HDMI so when I turn the Pi off it stays off? I don't want to have to unplug the HDMI cable every time I turn the system off.