My vertical position image on my nanao chassis is not able to be adjusted. I can't move the image up or down. It's not the controller either because I tried another one that I know works and that one doesn't work either. It looks like it wants to move and shifts slightly but never really moves up or down. Any idea why it's not working? The V size and horizontal size and position all work fine. Just V position doesn't respond. Any ideas would be greatly appreciated.