Sheesh, how embarrassing! Jimmy, when you're done touring, I'm sure Alembic will hire you in the tech support department; it seems the mounting nut had indeed been loosening slightly evermore in the past year and a half (as my performance schedule had increased), and that was indeed the problem.
My sincere thanks for the suggestion, JJ, and the next time you're in central NJ the beer/whiskey is on me......
Happy Thanksgiving all,
Chris