Does the "hour meter" record true clock hours, or does it depend on the engine revs? The answer seems to depend on the age of the tractor. Kubota has used both types of clock, but the consensus view is that when the BX24 and LCD displays arrived, Kubota went with "clock hours". So once the key is turned, the clock starts running at a constant true rate regardless of engine speed.
If the meter stops (i.e. shows the correct value but stops increasing) trace the wires from it. One owner had this problem and found a cut wire at the alternator.