Spider come off partially

[Lost Legacy]

Sub: 12" Fusion Powerplant

Monoblock: Fusion AM-NV 2500.1

So for the second time my spider has partially come off of where it is ment to be stuck down. It looks to me like the glue has failed (...again) but i'm not sure if that is the cause, or a result of something else.

I'm running just under the RMS the sub can supposedly take (set gains via some maths and using a DMM), and i haven't ever turned the volume past 3/4 on the H/U.

Any ideas what might be causing this to happen?

Sub doesn't run hot, amp doesn't run hot, no funny smells, just randomly started to make a "rattle" like noise that upon looking at is the spider slapping about because it's not stuck down

Thanks for any help