I've had a problem with an 11 year old UP2. In cold weather, the internal spool valve that shifts (after the doors are open) would stick. I opened it up, lubed it, but figured I nicked an O-ring. I called Phil and he asked me to send it back to make sure it worked perfectly and he'd replace the O-rings. No problem, and I bought another one to use while it's away. I have these valves in all my jets. Phil provides great service and has an excellent product.