Instead of fighting the fog with heat you can just wrap a hand warmer around the lens barrel with a rubber band, way cheaper than those strips. Point the lens slightly down between shots too, since dew settles on whatever faces up.

Ugh, I did the exact same thing for like two years until my sister yelled at me.

That "only shows up when the cabin was cold" detail is the whole clue right there, because cold shrinks metal and pulls that chafed spot tighter against the clamp until it finally makes contact. I do a wiggle test on every harness run before I touch a single box, grab the loom at each clamp point and flex it while someone watches the fault light. Nine times out of ten the short is sitting right where a zip tie or clamp was pulled too tight at the factory.