How long have you had yours for? Is it slowly going away?
I had a couple of replacements for screen issues - some make this noise, others didn't. My current one honest thankfully. It is just the rubber.
Wait, did I understand you correct that you did replace units because of this noise?
Ok so it seems a fair amount have it then. Does anyone else have it/not have it?
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I used a small cloth with saturated isopropyl on it left over from a screen protector and the only thing that came off was some black stuff on the cloth. Sound still remains.
Are you sure?