Camera being used by another application?

I have an iPhone 8 Plus, and I have never had any problems until recently. Anytime I use FaceTime with the front camera, after about 15 minutes, my screen goes crazy (turning purple, green, and freezing altogether), and the message "Camera is being used by another application" comes up. I have done all of the "helpful" tips and tricks in the articles even with the help of Apple Support via text, and I have been told "since we have taken too many steps with you..." I have completely rebooted my phone after a factory reset. And even with no other apps running, this is still repeatedly happening. Even with nothing else accessing the camera it is still repeatedly happening. What can I do to fix this?