Barry, is it possible that the buzz has something to do with the bridge itself? That is, during the process of attaching the bridge to the body, could a little plastic sliver or scrap have sheared off and is now sitting inside the bridge (I'm assuming there's some kind of cavity there, which may or may not be correct), and rattling when the strings are struck or the top rapped with your fingertips? Of course, if that were the case, I guess you'd hear it rattling around if you simply held the uke out and shook it. The only other thing I can think of is the reinforcing "collar" around the soundhole, if somehow it was set in there less-than-securely. Definitely a mystery!
