sub clicking

Got a American bass xfl. Makes a clicking noise once it gets moving. Not a scratching noise. Can push cone up and down and all feels smooth, no noise at all. Can see the coil, still a bright copper color. Just as loud as it ever was.

Dust cap is firmly in place. Tinsels can't be slapping due to design. Can't put a dmm on it at the moment, garage burned down and my dmm is mia.

Any ideas?