I had that problem with my 38n. After trying everything you did and more, I gave up. When it did work it never got me to actual level anyway and always brought me higher than necessary. So, I stuck to manual ever since. I was told at one point that because of the age, there was likely a bad item on the board and since I was better keeping control of it, why bother!
Just me rolling along in my land Destroyer!
04 Fleetwood Bounder 38n