I have had this same problem for many years. At first the high beams would ever flash, then I'd jerked the stock vigorously (pulling the stock hard and releasing it) and it would start to work. Its a persistent problem but at least I have a walk around. The contacts might be dirty or lose or whatever. It hasn't bothered me enough to take it apart and inspect it since I rarely use it. Try giving it some tough love and show it who's boss