I have a light i made my self its a XHP50.2 with a boost driver it does the same thing. Even if the threads look okay i clean them and it goes away. Its caused by high resistance some where in the circuit and that is usually in the threads in my case. It could also be the side switch?

Yea i done heaps of reviews for Rofis in the past but i have no contacts there now but they do see a few people come and go so its some times hard to get a response from the same person who knows what is going on.