Krups EA series -- error 06 /piston wont go down

Hey guys, just wanted to write this post. I had a Krups XP 7220 (It's like an EA model inside) and I struggeld a lot fixing it. When I turned on the machine started autotest, but it couldnt do and gave me the error 06 on the screen. I checked the water level sensor and the cable for the flowsensor, and i cleaned the whole water pipe system with vinegar. I even disassembled the hydraulic arm, but this wasnt the problem. Then I tried forcing down the piston when autotest and disconnect the flowsensor and it worked!! So the problem was in the hydraulic ULKA pump. There was a dried up o ring, the plastic ball was ok (4mm). So the ball was creating pressure but the o ring allowed the water to flow back. When the piston would reach the bottom, the pump wouldnt allow any water to pump, and the flowmeter detect there is no movement. Also when I did the autotest with the broken o ring, There wasnt full pressure so the coffee water wouldnt come out on the port,but in the dip tray, and the new ring soved this problem as well.
I hope help anybody, have a great day!:D