Load test the battery. Free at any auto parts store.
Check your + and - cables for cleanliness and tightness. Polish your frame ground point to bare smooth metal.
Bench test the starter. Use a propane torch to heat it up next. See if she starts when heated.
Replace the starter relay for sure. This takes all the current and those contacts really suffer. Mowers not so much. Bigger starters yes.
No. Something is getting hot and not passing current to turn the starter. Find out what it is.
Not on a starter, that I've heard about. Since you have a Diesel maybe??
That manual only covers the mower. You have an engine slash starter problem. Your engine is not cranking when hot.
Just to clarify, it will NOT CRANK the engine over, when the engine is hot right?