Screen refresh rate issue on 12 pro max

I have an iPhone 12 Pro Max and I’ve been having this persistent issue where the screen refresh seems to lag and lines show up on the screen (only a couple lines for like half a second)

Is this an indication of another issue?

The app icons also occasionally disappear for like half a second and show that whitish gray icon you would see in developer tutorials.

things I’ve done:

1- restarted the phone (normal and hard)

2- reset the original factory settings

3- dug around in settings to see if there’s anything that might be doing it? Couldn’t find anything

exchanging the phone isn’t an option right now as I’m overseas for a couple months and I do need my phone and there are no Apple branches here only resellers

so if anyone solved this, please help me save what little sanity I have left lol