How much approximately do you pay for the screens? Also is there non-transparent black tape put behind the soldered backlight cable (This is soldered on the digitizer ribbon cable). If it isn't you will see 3 vertical soldered points that isn't covered by black tape. This may be the cause of the issue.
Have you made sure that you have plugged in the front display ribbon cables correctly where the cable plugs themselves are not concave? You can check this by looking at the metal part of the display ribbon plugs. If it is you can use your hands to flatten them so it contacts better.
Could be a bad batch of screens or your supplier went bad.
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