The screens are suffering from 'burn-in'.
https://metro.co.uk/2023/10/17/iphone-15-pro-max-hit-with-burn-in-as-users-screens-malfunction-19677263/?utm_source=dlvr.it&utm_medium=blogger
https://metro.co.uk/2023/10/17/iphone-15-pro-max-hit-with-burn-in-as-users-screens-malfunction-19677263/?utm_source=dlvr.it&utm_medium=blogger