I've got a nasty buzz at the 1st "fret" on the D string on my fretless. The other strings are fine in this position so I don't think it's something a truss rod adjust would fix. The buzz only happens on the D string exactly where I need to put my finger to play an Eb in tune. If I move my finger slightly up or down the neck there is no buzz. Is this something I can fix myself? Is it as simple as sanding the fingerboard just beyond the buzz? I don't mind doing it myself but I don't want to make it worse.