After screen replacement LCD flickers black?

On an iPhone 7. So the screen replacement went well, and only a swap from one unit to another. However this weird flickering started shortly after. The thing is it only occurs when receiving/sending a text, or when initially turning on the phone(when the phone first searches for service). Or when a sim card is first inserted, and goes away a few seconds after service found or text sent/recieved.

It reminds me of older phones when near computer speakers, you send a text and the speakers make a weird beeping interference sound. Except it's affecting itself instead of the stuff around it.

I've tried a dfu restore, reseating the connectors, I've checked to ensure every screw is tightened down properly, tried a new battery and this screen was working perfectly fine on the other unit.

Any ideas at this point would be helpful!