My car once developed a fault with its indicator stalk switch that also flicked a high beam, i.e. when you want to flash someone, so I didn't realise until one bloke shot off in front of me from a side road, I stopped with emergency brakes and started to curse the bloke, and he cursed me back saying that I flashed him to proceed!
Did I ? of course I did not, but then a few nights later I saw my car's headlights were going hay wire, and realised that my car was flashing randomly!
Faulty indicator stalk assembly .