So this is quite a bit after you had your problem but some people may still be reading this tread. We had a similar issue. The
razor could wash a 300 cars without the arch not completing its trip to home position or as little as 20 washes. We changed prox's , sensor wire, All in all about 900 dollars in attempts to fix this issue. Then Mark from our local
washworld distributor told me to do something so simple. He said that wherever the helicopter is on the proximity sensor, to move it on or off by 1/2". The move was made and have not had a repeat problem in over a year. Having said that the move fixed the problem sounds ridiculous but it could have been that the screw holding the star might have been a tiny bit loose or just the slight movement of the star plate did. Anyway, it doesn't take much effort to try this.
BCM