Screen blacking out every 3 seconds after replaced LCD

I replaced the LCD and digitizer on a Nexus 6p. After the repair the screen blacks out for 1 second, every 3 seconds. It doesn't do this during the boot up or the recovery mode screen, but once android is loaded up it does this consistently.

I tested a second screen with it which worked fine, then the second I put the back onto the phone it returned to the blacking out every three seconds.

My guess is a short happening somewhere, but I can't determine where or why it only happens once android fully loads.

Anyone have any thoughts