ronin welcome to the club.
it'll do that clean or dirty.
the barrel cycling sloppy is normal. the way i see it, as it finishes cycling the flare at the end of the barrel is 'corraled' by the hole in the slide for stability before firing again. that's what causes the scratches at the barrel flare.
i bet the barrel actually jumps around a bit when going forward during cycling, and somewhat bobbles it's way forward til being corraled, rather than a perfectly smooth forward/backward action. i could be wrong i guess, since it happens to fast to see of course, but with how sloppy/loose the barrel is til full cycle or in battery, i thinn i'm correct.
pull the slide back just a bit and the barrel gets sloppy as soon as the barrel flare comes back out of the locking action of the slide hole.