Green Screen on 15 Pro Max

I had an issue with my 15 Pro Max. It started suddenly as I was using it and contacted online support for assistance, and they asked to hard reset the phone. The issue was resolved for a few hours and it started again. So they asked me to take it to a local service center. The service center is saying that it will take 15 days to fix the issue and return the iPhone.

Also they commented that it is the first time they are having a customer with a green screen issue with iPhone 15 series.

My question is - why is this happening with Apple frequently and what are the actions taken to address this?

Also does it take two weeks to fix this issue at the service center?