My Gerber Ultra-flush system has stopped flushing. It tries to flush, but nothing much happens — a little noise, water runs for a nano-second. The weird thing is that if I turn off the water, drain the tank, turn the water back on and refill the tank, it will flush 1 or 2 times. Then it stops flushing again. I have replaced the cartridge, and am wondering if I should replace the upper and/or lower group parts as well. I have to special order them, as nobody seems to have them in stock around here. I can’t even find a plumber who knows anything about them in this area. Thanks for any suggestions, martha