Hopefully parts chucking solves the problem. In case it doesn’t:
Have you inspected the wiring? A chaffed, always hot, wire contacting a chaffed intermittent hot, attached to a relay or switch, can cause voltage to pass to a circuit that should be cold. Don’t rule out a shorted relay socked. These could also be temperature sensitive.
The only other thing I could think of is that something crazy is going inside your starter solenoid like a broken bus bar or spring.
Have you inspected the wiring? A chaffed, always hot, wire contacting a chaffed intermittent hot, attached to a relay or switch, can cause voltage to pass to a circuit that should be cold. Don’t rule out a shorted relay socked. These could also be temperature sensitive.
The only other thing I could think of is that something crazy is going inside your starter solenoid like a broken bus bar or spring.