Next time you go out, arm yourself with a few troubleshooting tricks.
Since it has a magneto, that as you suspect, might be failing, carry an extra spark plug & set the gap on it at .045".
Leave all your spark plugs installed, and when she fails to restart, pull any of the spark plug wires, plug your spare spark plug into it, and wedge the spark plug between the port side exhaust cover (acting as engine ground for you) and the spark plug wires.
Attempt to start the beast, and see if that test plug displays spark.
If you have a very thin spark, it might not be enough to spark under compression.
If you have nice fat blue-white spark,...
Reconnect that spark plug lead to its installed spark plug.
Now,...Spray a generous amount of carburetor cleaner (not "Starting Fluid" which is ether & can destroy a 2 stroke engine in a nano-second) into both carburetors, and see if the beast attempts to start.
If, with this test, the beast tries to start, consider going through your fuel delivery system, and see if you can identify a restriction.
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