This happened to me once - I was in people and hit he phone number of a contact by mistake and the phone started calling. Unfortunately, I hit the power just as it started calling. Once I did that, the phone was never responsive - it just started completing the call.
It only happened once, though.
I do have the Verizon screen protector on, but it definitely had a cutout over the proximity sensor.
The Verizon screen protectors are the worst ever.
The zag ones are overrated in my opinion as well. They add a vinyl, rubbery feel that I just do not like, although they do look pretty clear.
The best one I've found by far is from a company called Ismooth.
It is literally unnoticeable and feels like the actual screen. It is also pretty good when it comes to scratch resistance. And I've also never had a problem with the screen blacking out while on calls. I often put my phone in speaker and use other apps while on calls.
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