I have recently bought an mip cvd kit my my nr. Not a week later the cups were slipping. I tried to tighten the screws, but it got losse after 1 minute. I put some thread lock on the screws. It work for a week. When I tried to remove to the screws, the head of the screw started stipping. So now I have to buy a new pair. DOes anyboy know how I can keep it from stripping the head, and also how to avoid slipping.