Distinguished SOTW Member, Forum Contributor 2014
Just a suggestion here, but I recently worked on a horn that had a tendency to gurgle on low D and also seemed to want to jump an octave on middle G. I checked it for over an hour with a leak light, and nothing. Next I took a good look at the octave pip on the body and neck to make sure they weren't leaking at the solder. Again nothing. I then figure maybe the neck is leaking, but The neck was a very good fit in the tenon, so I decided to expand the bottom of the neck to make sure it was sealing for sure. Voila, there was a very small leak around the bottom of the neck that was letting air escape. Just thought I would post this as a useful note, that when everything else fails in this situation take a look at the neck seal, because even if the neck fits tight at the clamp, it still could be leaking at the bottom.