CIS admin gives you a very good option, but as you might have noticed it does not change the need to continuously have to go through the head cleaning process. Very simple answer based on other forums and personal experience, this type of system is designed to be used continuously therefore, it will be a problem that has not been corrected because you have to first think about physics and simple hydraulics. Has anything changed since your last air vent plug removal? btw, which one did you move? the one in the back of the cartridge? or the tanks?