They fail quite often. OP's case sounds like the hundreds of cases I've read about over the years, probably needs a new solenoid. There is no off the shelf fix from a hydraulic shop or parts supplier. New or rebuilt part needs to come from HWH. As for failing when left in retract mode, it's HWH that sets how long they stay on, just doing that shouldn't cause them to fail, but it appears that it does. Reading all the cases of folks having to replace them, I have been very careful over the years I've had mine to never leave them on too long, and still have had failures.