iPhone defaults to hello screen

Hello!! My mom and brother now have this issue re-occurring again. When they wake up in the morning their iPhone screen has the white hello screen that says hello in various languages. The worst part about this glitch is the fact that it prevents any alarms from going off or text messages etc because it is locked in a hello screen and she has to type in her iCloud password and such to get back into her phone. It doesn't happen every night but happens here and there within a week. I posted a while ago in a different forum within apple forums. Since then we have wiped both my moms phone and my brothers phone and re installed through a backup of their device. I can't seem to find a solution anywhere! Any thoughts?