New Green and black lines in the notification bar when i join a match

[LongGolie8]

My brother has Xiaomi redmi note 13 pro 4g when he is join a match in games When he pulls down the notification bar, green and black lines appear for a while. The phone is new, he bought it 2 weeks ago, it has not been dropped. Anyone knows why is that happening

 

[ciubex]

And are sure that on the phone is flashed xiaomi.eu custom ROM and not the official stock ROM? Because this forum is not an official Xiaomi forum.
Anyway, have you tried to enable or disable turbo mode and checked if is any difference?