The problem I had was free-swimming pellets in the boil kettle plugged it most of the way while whirlpooling and then chilling (with an IC) such that the post-chill lautering never had a chance to finish. As soon as the first bit of mesh was exposed, that became the preferential path to the pump, and it cavitated within seconds, never to recover.
There were still four gallons of wort in the kettle, so I lidded it and let it sit while I cleaned everything else up, then siphoned the rest off the hop mush into the fermentor. Pretty much a horror show compared to my typical brew day, so it was one-and-done for the hop stopper and I switched to a 6x20" ss spider. Which is too bad because I really like the idea of free-swimming hops in the BK without plugging the hell out of the system...
Cheers!