Most likely the ignition module is beginning to fail and has becoome temperature sensitive. Here is the wiring diagram from the LX188: View attachment 282789
...and attached below is a manual excerpt on the ignition section...
If you think something is causing a 'heat related failure' you can induce that failure using a heat gun trained on the suspect, assuming that you can get to the suspect component. Conversely, you can cool that component with compressed air (to wick the heat off) when it has reached it's failure temperature.
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