Was turning the locking knob on top of filter and realized while the knob was turning it was just coming out of the top it wasn't loosening the lid. Kept turning to loose and the locking knob came all the way out. It screwed back on to the rod no problem but can't get the lid off to clean the filter cartridge at this point. What needs to be done to I guess make sure the locking knob is attached to the lid so the lid will come off when the knob is loosened? And with the locking knob off should I try to sort of pry the lid off with something like a flat head screwdriver or am I just going to cause more problems? Thanks