After 3 years of frustration with my Magnum 725 54". I went through all the trouble shooting, took it in finally and it cost me 400.00 and they replaced things that I already replaced except the starter. Which at the time was only a year old. What would happen is what you described. Additionally, I would hand load it and disengage the neutral engage/disengage arms to roll it, once on the trailer I re-engaged them and set the park brake. I took it to my nephew to look at it. He sat down and it started right up! Grrrrrrr..... Took it back home mowed about 100 feet, got off to remove debris, tried to start it back up and nothing, dead as a door nail! After lots of loud meaningful Army type words of encouragement to the mower I pondered. Hm.. it starts after I disengage and then engage the neutral engage/disengage arms. I inspected this and found that the one on the right comes out of the slot and wiggles loose. So I tested that theory several times and that is what it is.Even with the keeper pins in the last slot to prevent it, it will still do it. When I get home today, I'll see if there is an adjustment I can do or some other way to keep it from wiggling loose and disengaging my mower!