They use the word 'permanent' but in reality environmental conditions (low humidity) along with mechanical pressure (in this instance the constant movement of the clip up and down) could eventually sever the material.
Guess I'll goop it on a bit heavier and hope for the best ...
Maybe you would have opted not to use metal channels now, or perhaps you would have found a rubber clip system, etc.
Yup! If it did it again I'd skip the clips and maybe the channel. BTW the life-time of rubber is also limited ...
Grab that sub and crank up some low frequency noise in the room and see if anything else rattles before you close it all up.
The problem with that is you need to close it up in order to check it
I guess you could close in one layer, check, and then do the next ... but each layer changes the dynamics
