Shadowy Dots on Screen in Rear case but not if it is out

I just changed the battery and I connected it to see if it was ok and there is 1-2 black dots showing up when I press near the spot. But if the screen is out of the case it doesn’t happen. I looked for parts that could be pressing against the back of the screen but couldn’t find any. P.S. anyone know how to use iPad Air 2 Cellular adhesive strips on the WiFi version? I emailed IFixit support and they said it was possible but didn’t say how.