GFO Reactor Problem

[gregzz4]

I always rinse mine in a mesh bag (probably 8gals of RO) over a bucket, and I run my outlet into my sock chamber to catch anything that may get past the foam

Not sure what happened in your case but I know that if mine were not rinsed well it could have happened to me
I used to get GFO back-siphoning into my return chamber when the reactor pump was turned off

I now have the TLF NPX filters between the GFO and sponges and pellets no longer escape

Only other thing that comes to mind is too much flow through the reactor ?
This will grind up the GFO, even if you rinsed it