I suspect the powder you are using has stubbornly built up undetected carbon in the flutes. A major chamber scrub and dry swab after, might be a good thing to start with.
If it is a JLD or PTR built rifle, I doubt it is a mag wobble issue etc. Maybe, but doubtful.
Good for you about being satisfied with the rifle headspace settling at .010. That is a non issue I believe and refreshing to see. Good luck!