Pics of the patient might help stir some ideas. Fret buzz from a fretless is a head scratcher. My last 'unexplained buzz' turned out to be a loose screw on the tuner's head.
The action on most commercially made ones I have seen has been rather high. I have not seen one with decent acoustic volume.
I put about 3mm action at the nut and 6 or 7mm at the 12th on the one I made.
Hi guys, thank you all for your thoughts. I have now changed my strings and the buzzing went. it must have been the damaged string.