Had problems with burner flames so decided to clean all four burner systems . Successfully disassembled and cleaned rear 2 burners and front right burner. HOWEVER, I've encountered a problem with the front left burner: the VENTURI cannot be removed. I was able to unscrew it about 1/4" and that's it. It is now freewheeling but cannot be moved either up or down using socket wrench.
What is stopping the VENTURI from coming off?