Edstrom watering system help

So for about 2 months or so now I've been using the Edstrom / Agselect watering system. It it really covenient and great, except that I'm having problems with some of the valves. Some of the valves work great, and when I press the trigger water pours out. Others have to be pumped a little before the water comes out. Also, the biggest and more irritating issue is that randomly, a valve will just stop working even though the line is receiving water. I've contacted the company, who sent me five new valves to replace the five valves that had stopped working at the time I contacted them, but now I have several more that have stopped working. I don't understand why. Has anyone had this problem, or have any suggestions? Also, is there any way to make the valves that are slower to release water work better?



Thank you!!