I know we have discuss this before but I had my first case of this myself where ignition switch causes magneto coil failures.
I been working on a Giant Vac Giant Mow where it has a completely reworked electrical harness. Previous wiring harness had a complete meltdown. I personally did not do the electrical rewire.
The mower was brought into my shop after it was pulled from another shop. I manage to get it running after carb repairs. It just came back in after several weeks where it would not start. Looked like a simple coil failure on an opposed engine. Replaced the coil, started the engine, and called the customer for pickup. Well the customer came by Wednesday morning started the mower and it ran well like crap. I went over to see what over and it just keep getting worse, started shooting out flames from the exhaust.
I apologize for problem and got the customer leave it me to find what was going on as I had another customer on the yard at the time. Well when I got back to it I found the ignition was out again. Double checked by unplugging the kill terminal. I set out looking for a possible cause remembering that a voltage surge via the kill terminal can cause this failure on new coils.
I did find a voltage problem but not the usual monetary application of 12vdc switching contacts. I actually had a 1.5 vdc voltage on the kill wire when the ignition switch was on and normal ground in off position. I made sure there no voltage was on the line with the ignition switch unplugged. This was a high resistance voltage leakage as I was able to pull it to ground; just enough current to take out the coil's electronics. Strange that a new switch would cause this but I suspect rain water had somehow gotten into the switch.
Just a reminder to me at least to check the kill wire for voltage when we have a magneto coil failure.
I still have a charging in my opinion but I unable to remove the flywheel due previous removal where and hammer and chisel was used then an impact to tighten the nut. Normally I can get most stubborn flywheels off but not this one. The customer will just need to recharge the battery as needed.