Blurred screen when using phone app

I am trying to remotely troubleshoot the issue with a iphone 7 for my 75-year old father. I see the blurred screen and it is only when using the phone app. A soft reset clears it only for the first time that you open the phone app. Once you have gone to the home or used another app, the blurred screen in the phone app re-occurs. This is not a situation that a more senior user can quickly and easily deal with especially when in a time-sensitive situation. I see chains from late 2017 but need a firm and final answer.