Difficult buzz problem
 

Apologies for the long explanation.

I have a piezo-only fretless 5 (GraphTech ghost piezos in a Hipshot bridge). Was using SIT Power Flats without a problem, but also without a lot of enthusiasm for the sound. Strung up some TI Acousticore's - fantastic sound, but at the cost of an odd buzz on the 'E' only. Seems to be coming from the bridge area, but difficult to localize. Buzz is present with open and fretted string. With other strings (the Power Flats, TI Jazz Flats, LaBella tapes) the buzz does not occur. Replaced the Acousticore 'E' - same thing. Changed out the piezo - same thing. Can't alter the piezo saddle itself - such as filing to alter witness point - without ruining it (according to the manufacturer). Adjusted the saddle every way possible. Can't find anything wrong (cracks, loose crap) with the bridge, controls, cavity, etc. I, a very experienced luthier, and a couple of techs are stumped. As is the piezo/saddle manufacturer.

Any suggestions will be appreciated. I'd really like to use the Acousticores.

I'd hazard a guess that TI has had a bad run of E strings. I'd contact them directly.

You may very well be right. I'm having a hard time coming up with an alternate diagnosis.