Aaron,
Good afternoon! When the screen was replaced, was the ear speaker/proximity sensor transferred from the old screen? (more than likely yes, but always like to ask) If it was not, that is your issue. Those need to be with the original board. [br]
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From what you are describing, your phone is ghost touching. More than likely the result of a defective screen. Be very careful about your lock screen with the phone ghost touching. That security message you saw is just the first. It will then lock you out for 15 minutes, then 30 minutes, then an hour, then one more chance. At that point the phone will say “disabled - connect to itunes” at which point your only option is a factory restore which zaps all your data. With the ghost touching, the phone could type your passcode over and over in your pocket without you knowing. [br]
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Best advice is to get another screen and give it a go. I see a lot of defective XR screens in my shop.[br]
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Hope this helps!
Roy