I’ve just had the same issue with an iPad Air where there was a rather frustrating bit of dirt caught between the digitiser and the lcd and wouldn’t move by just lifting the glass with a suction cup just a little and flicking/tapping the glass so I cut a thin strip of the plastic film that covers the adhesive on the back of iPad batteries (about 0.5cm wide) then heat the side of the digitiser just enough to lift it a tiny bit and then insert the plastic film making sure it’s perfectly clean and slide it in to where the bit of dirt was and simply swipe it away and now it’s perfect again.
Just need to make sure it’s clean and you don’t smudge any digitiser adhesive onto the digitiser or lcd.??
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