Weird pixel glitch on my phone screen when viewing videos

[Theokitsuragi]

So I've been having this issue (Pictured in post) where when viewing videos, etc, a pixel glitch starts to consume my screen and I have no idea how to get rid of it. Workaround right now is closing and reopening the app or as I've recently found, taking a screenshot.

I've tried updating my apps, my OS, restarting and letting my phone go to 0 before charging again. Nothing's worked so far - Please help!!