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I have the same phone, and it happened for the first time like 20 minutes ago! It wouldn't focus on anything. I had to close it, and re-open.
 
I keep hearing about this, but I have yet to experience it. I think my GF did once on her 7, but I haven't on my 7Plus. I set the phone up as new.
 
It happens now and then on my 6+. Seems to be connected to ios10, because it didn't happen before, on 9. Report and hope they fix!
 
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