Nova 13 Pro Lag and Screen Flickering during Downloads

Whenever I download something or when there's an update in the background, my phone gets super laggy until the download is finished. Additionally flickering will appear in the shape of one or two purple/slightly greenish vertical bars at the bottom of the screen (which are not visible on screen recordings).

Since I can't find any info on this issue online, does anyone else experience this with their Nova 13 Pro or Huawei phones in general? Any idea on what could be causing this and whether there's something you could try to fix it?

The phone is fairly new, I never dropped it or anything. It's quite annoying, because besides this one thing I am happy with it.