Originally Posted by
Philphool
If all else fails, look at the saddle. I had one instrument like you describe and finally noticed that the slots for the A strings were made with a downward angle towards the forward edge. Thus the take-off point for the string was not the forward edge, but maybe a half millimeter back. This allowed the string to vibrate against the forward part of the saddle slot. The amount of angulation was very small and hard to notice.
Leveling the slots (or actually adding a very slight ramp from front edge to back) solved the problem.:)