Before you go through a bunch of calibration, I’d see if it happens with a different filament. Those black particles there are likely something with a higher melting point than the surrounding PLA, otherwise they’d “smear” during printing. I’m betting you’re hitting some intermittent clogs. See if the problem happens with a single color filament.

I subscribe to !newcommunities@lemmy.world which helps. Other than that I look for mentions of other communities in comments, similar to how I used to on reddit.