Sounds like a dirty or knackered column switch to me. Might be worth taking the switch off and giving it a blow out and squirt with wd40 . If not it may need replacing but check all your earth connections on the headlights / switches first as they are not a cheap item. Looks like Custom and Commercial can get one within a couple if weeks or worth putting a wanted ad on here for one as someone might have a good one going spare.