wow, that sucks to hear. i've never had any prob's with any of treo's stuff. i know those subs were good when i sent them to you, you shouldn't have to worry about used. my integrity is worth more to me than a few bucks. i would not have sent them to you if i thought there was anything going bad in them. i know you aren't saying that, but want to get that out of the way.
if your coil was letting loose, just pushing down on the sub wouldn't make the problem go away.
check everything that no glue joints are letting loose. spider to basket, dust cap, and make sure your box joints are solid. any flop between panels seperating will rattle like a blow sub also.