This is an ACTG1 Eastman 23.5" scale acoustic with an advertised dual action truss rod. I had lately noticed a buzz and initially thought it was the wires of a JJB pick up I had installed. Upon gently shaking the guitar and holding the neck to my ear, I noticed a quite audible rattle. The neck is straight and where I want it. I tried to adjust the rod and it definitely loosens and tightens but the neck stays the same. Could the the truss rod have come undone? I did adjust it slightly (looser) when I changed strings to a lighter set of 11s from 12s. After these attempts, the rattle is still there, when shook, but the playing buzz has diminished. This buzz is most noticeable on the open B string. Bummer?