You're certain that the upper pip is seating quickly and properly when you make the transition from it to the body pip? And you're certain that the palm keys seat immediately? Forgive me for such questions but I know on my old Buescher pre True Tone I was tormented for years only to discover that the D palm sealed perfectly under the palm keys spring- but did so only after a half second or so. It'd contact the tonehole slightly irregularly and leave a hairline leak for a fraction of a second before settling in. This led to similar issues with cracking when going down but not when playing under other circumstances and caused me no end of aggravation. Leaklights only revealed it when I specfically let it close while watching- and it olny leaked for a very very short time. Normal checking showed it perfectly closed. But that fraction of a second was enough. Analogous to the "if I can make it seal by really tightly gripping the pearl does that count as a leak?" on a normal stack key but a little more insidious.