Oh man, gross! So glad you tracked it down at least. Now I’m wondering - what exactly were you doing as SOP? (Wondering if my blichmann plate chiller is also filled with gunk)
My process is to have a kettle full of strong PBW solution (typically room temp - often from prior uses) sitting around and IMMEDIATELY as soon as I’m done transferring out of the boil kettle I swap the hose from the boil kettle to the pbw kettle. I then turn the pump back on and push PBW until it runs clear.
Sometimes I then pump about 5 gal PBW into the boil kettle right then, and then pump another few gallons of hot water through the pump/chiller system to rinse it all out.
Other times, I let the PBW stay in the system while I clean other things. It might even hold the PBW inside for 24 hours before I get to it. Then I rinse out as mentioned above.