I have a 30x60 rectangle with Maxipaws in all four corners on one zone and two others half way down the 60' side of my rectangle. These are on a second zone. The two zone head works fine. But three heads on my four corners don't cycle properly. They stick part way though. One of the four works fine and it does not matter where in the zone I move it - it works. I'm using the 07 nozzle on all four. I have 08s on the two center ones. My pressure may be marginal. I read about 38psi at the PVB. It is very close to the yard area and everything is in either 1" pvc or 1" poly. How is the best way to measure pressure at the head? Would it help to replace the bearings? I see Rainbird has a kit available. Somewhat related.... what is the vane for? I see a diffuser behind a couple of the nozzles but not all of them. What is this for? Could this be any part of the problem? Thanks.