The only other switch that is not on my list is the operator presence relay......so check that.
Yes you replaced it, but does it work.....
OK now it is time to do come testing.
Pull the kill wire off the coil and test it with your lamp connected to the + terminal of the battery because as you should see the black wires are all ground wires.
They should be open circuit when you mow but go ground if you get off the seat without the brake on or get out of the seat with the PTO running.
So now you are going to check for ground at all of the switches ( both sides ) on that black wire.
Somewhere along the line one of them, or the wires that connect them are grounding out and killing the magneto.
Leave the black wire off the coil o prevent power going down that wire as it will fry the chip in the magneto.
The seat switch relay will only be energised when the engine is running as it is powered by the A2 terminal which in turn is powered from the A1 terminal that gets it's power from the alternator.
That connection & the diode between them is inside the switch & not shown ( like vital clues in a British murder mystery ).
Could you explain a bit more simple. Kill wire off coil? Where is coil? Check wire both sides black wire?? I look at some of these switches physically and see more than one black wire I'm not understanding, very sorry.
Black wires goes into a switch and out of one, "test both sides" means you test all black wires from one side of the switch to the other side....