The old Cav stalks had a habit of breaking the self cancel if you held the stalk down as it cancelled. ie. You want to keep indicating as you straighten up from previous turn and don't allow it to cancel. Nice crunch noise when it happens too!
Come to think of it, I did the same to an old Vectra. The stalk design seems to be very similar (if not identical).
No need to worry though. The new style Vectra indicators seem to come with the cancel pre-broken as standard!:lmao: Well, thats until you work out how to use them.