The seat switch is not the problem.
There is a switch above the brake linkage underneath and to the rear of the engine.
The actual switch is on the right side, underneath the fuel tank.
Grass clippings and dust tends to build up around the electrical connector, and if the mower is out in the rain, or you wash the mower, the water tends to short out the connections.
The switch may not be bad (mine was OK), but the grass mat that has collected has to be removed, and the connector removed and blown out with air, or whatever.
(This same condition also causes the mower to stop moving while the engine is already running)
I guess it depends upon which connections are shorting on the switch.