Weird green flashing on FaceTime

Just recently bought my girlfriend a iPhone 11 Pro Max and whenever we FaceTime randomly this dark green screen with lots of cubes flashes and goes away. It happens to either me or her but never both of us at the same time when we’re on the phone. She’s had a previous iPhone but this has never been a issue before, it only started when she got the new one. Is there a fix to this? The flashing isn’t pleasant and quite creepy.