Every now and then I run into something that's a real head scratcher. This Power Rain is about 4 years old. What is happening is that when the top bar drops at the front of the car it sometimes just sits there in the full down position and does not move. This happens only on high pressure. When applying presoak it works fine, and in the test mode it works fine. If the car backs off the inplace switch when this is happening and then goes back on, it will finish the wash. Have checked most all the usual suspects, i.e. down prox switch, loose wires, bad blood, etc. Any ideas?