Not exactly sure how these things are configured, but you might try this:
Shut everything off, wait a minute, turn on the tank, then open up up gar feed on the Q (this is the part I'm not sure of, are there two separate "open" knobs / controls?) , if that's the case, the safety valve reads it as a gas leak & goes into extremely low flow mode........you need top sort of build up a head of steam, so to speak, before full slow works right.....or, it's just still too crusty?