Yes it's very common. What happens is over time the contacts in the switch get worn down and the metal that is worn off ends up in the grease. It eventually has so much metal in it that it then becomes conductive and starts causing problems with the relay.

You can either remove the switch and disassemble it which isn't too hard. Use an electrical contact cleaner to remove all of the grease and you may find the the contacts need turning 90 degrees if they have worn too much. Then apply some new grease suitable for electrical gear or get a replacement switch from someone breaking a gti 6 on here but a second hand one may have the same problem. The other option is to buy a new one but you need to make sure you get one for dual beam headlights that the higher spec 306s have otherwise your high beam headlights won't work properly.

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When I've got time I forget what I wanted to do, and when I remember what I wanted to do, I have no time!