Sometimes it opens and sometimes it doesn't. I notice that the release catch seems a bit sticky - but the spring that opens the dispenser seems fine. Can the catch be cleaned/replaced and if so how do you get at it?
this has alot to do with your water pressure! you need to make sure your spray arms are clear by using something like a toothpick to clear the hole. Also run a pots and pans intensive wash with a Calgon tablet without dishes in. If none of tis works check your water pressure is spining the spray arms around as this iswhat opens your dispenser