Probably loose or wonky contacts within switch Chris rather than dirt or corrosion. Not desperate enough to take the old one to bits though assuming it was possible. Popular application for these light/indicator and matching wiper stalks is with Land Rover, some Freelanders for sure.

Richard

2018 Roadster 3.7
1966 Land Rover S2a 88
2024 Royal Enfield Guerrilla 450
1945 Guzzi Airone