Has anyone had any issues using their stock backup camera with an aftermarket head unit? I have a 2012 GT, and replaced the factory navigation head unit with an Eonon Android head unit, along with a Metra AX-MAZCAM harness with a step-down (12v-6v) converter like you're supposed to. The video worked at first, and now it doesn't seem to send the proper signal most of the time. I have done everything from reading the wires and disconnecting/reconnecting the wires in the proper places. Not sure where the break in signal is happening. When I put the car in reverse, it's just a black image with a "!" due to no video signal. Anyone have issues like this? Trying to avoid paying another $40 for an Eonon camera, but I may have to.