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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'm guessing this judge considers the telephone to be an example of negligent design as well. After all, the phone company doesn't record every phone call I make and disconnect me if I mention an illegal drug.