I would make sure you play every single note through it at a good volume, I have had rattles happen on A but no other note, I have seen with it several notes, usually A, on a couple cabs.
Other than that these are all pretty much what I was going to say.
Carvin LB76 / Dingwall ABZ ! Support Local !
Markbass SD 800
Epifani UL2-310 / Markbass 104 HF-4
! ! Rocking against all gods ! !