Wierdest backlight problem I've seen.

Alright so this might be the strangest backlight problem Ive seen on a phone. Hopefully someone has had this similar issue and can shed some light.

Got an iPhone 6 screen from a store with full backlight working on one aftermarket screen but no display. Again not dim, backlight is working but display isn't.

Here's the kicker. Every other screen I try on the phone, including known good original ones, show no backlight at all. Backlight will only show on this aftermarket one that was the original replacement for the customer.

I've ruled out backlight and am wondering if I should even go into display circuit (which I probably still will) if its having this behavior with every other screen tested.

Waiting on word to see if I can restore or not.

Any theories?