Coincidently, fwiw, I just took one of my...five Chudnow primaries apart to fix a creep problem this afternoon that had popped up immediately after a tank refill. Removed the cartridge - which seemed a bit loose - and found a bunch of teflon tape fragments (?) Your post prompted me to go check and it's steady as a rock now, so my best guess is the cartridge O-ring wasn't perfectly sealed to the body cavity.
Aaaaanyway...I removed the (dual body) reg from the tank, laid it on its back, totally backed off the pressure adjustment screw, and used a big arse adjustable spanner to remove the plastic body - counter-clockwise as you'd expect.
Top to bottom, from the captive adjustment screw there'll be a steel dished insert followed by a spring, surrounded by a brass ring that interfaces the plastic shell to the diaphragm that seals against the metal body. Under the diaphragm is the cartridge, that threads in clockwise as expected, and has a rubber o-ring on the back to seal to the port...
Cheers!
