I've done setups on my basses and guitars for years...I know the fundamentals, but my new AmStd Precision5 has a problem I've never run into. It has very even keel, low action all over. Plays great--not even buzzing if I dig in a bit. EXCEPT...on the A string starting on the 9th fret (and up to the bridge end of the fretboard). It buzzes unless I EVER so lightly play. Unlike the entire rest of the fretboard, which I can dig into and not buzz--actually the best of all my basses for that... I've tried rasing the A string saddle, to the point that the action is significantly higher on that string than all others...yet, it makes only a slight improvement in that area. If it were a raised fret or a relief issue, I would think I'd see it on other strings...if the 9th fret were low, even just on that string, it would go away on the 10th, which it doesn't. It's like magic--8th fret=fine. 9, 10, 11...and on...BAD buzz. thoughts? Advice? things to check? it's just something I've never run into...and on on a bass that's actually the best playing 5 I've ever played otherwise.