Dose the engine have a low oil safety switch ?
Some of these ground the magnet so the engine will not run while others prevent the engine from cranking so you don't sieze the crankshaft ?
More than once I have done a call out only to find a mower with low oil on a slope.
Swung it around 180 so the oil on the sensor side was higher & off he went.
This was a Dixie Chopper but a lot of mowers use engines with oil switches on them
Some ring buzzers
Some kill the engine
Some prevent it from cranking
IF the oil level is right on borderline then when running the level in the sump drops that poofteenth enough to activate the switch
Left sat for a while, all of the splashed up oil returns to the sump raising it that poofteenth enough to deactivate the low oil switch.