Not seeing this on my M1, Maighty. If possible, I'd try different footage from a different camera in a new sequence to see if you have the same trouble. It looks as if you're having some other GPU artifacts appearing and that doesn't look OK either. Perhaps you are overloading the timeline with too many effects or the footage is not decoding very well. You can also try the Beta version of Premiere Pro that does better with some of the newer Sony XAVC formats. So, check that out.