Pulled the indicator stalk out of the wife's Lancer, no corrosion, so back it went.
Easy job, 2 philips head screws, massage the plastic top and bottom column covers to unclip, unclip stalk. Look at connector.
Didn't think of adding some sort of corrosion inhibitor, maybe when I buy some first.

Dielectric grease, not resin, I'm guessing.
Definitely worth checking though, but not worth booking and hanging around the dealership for half an hour.