This sounds like a faulty display assembly or possibly even just a poorly seated cable. If you can, try to pop off the display connector and give both sides a gentle clean with some high % isopropyl alcohol. If the screen is still unresponsive, it’s likely to be a bad display assembly.
And unfortunately if the same behavior is present on multiple displays, it’s possible the board was damaged somehow during repair, in which case, you may want to look for a new device or send it to a board repair service.