This motor is just killing me. 4 years in a row in early spring a major malfunction. So my trim gave out on me this past weekend. It goes up fine but can't go all the way down. My mechanic just called and said it was not fixable and I need to replace the unit. He said air is getting into the system and the oil is ending up where it is not supposed to. He mentioned something about a shuttle valve. Anyone ever heard of this? Do I need a second opinion?