Seems the best way to describe it. There's a copy of top of the notification area 2-3 pixels high at the bottom of the screen when the tablet hasn't been shut down for a while. After powering off and on again it is okay. This is a mild annoyance though as it shouldn't happen. I've tried using different launchers for the home screen but they all do it eventually. Also after a factory reset it will come back eventually. The screen and tablet generally works fine otherwise. I think it's a ROM issue rather than hardware. Any ideas? See the photo linked to below rather than screenshot because the screenshot looks normal. So the issue is what at GPU driver level if anywhere.
https://drive.google.com/file/d/1LH5FDpFXvIBPOgX77wFZZRHqrsKKrz8u/view?usp=drivesdk