Is it normal for my 2 month old G3 to have the heads move up and down (front to back) at different speeds? The install tech didn't have enough time to solve the issue in head 2 and M&R sent a complete new setup. This didn't change anything but the second tech found that when a plastic washer was loosened, it "solved" the problem. Now I'm having the issue show up on different heads and I'm trying to figure out what is causing it. Would a screen cause it for some reason?