I've had good luck with them so far. I can tell you that the needle valves tend to trap dirt. On the first one I had for my Panther, the gear was moving VERY slowly. I kept backing out the needle valve until it finally came out. It poped out with the air pressure and a little black ball of crud came out behind it - problem solved. That valve has worked great since. You might try taking the needle valves out of yours and seeing if there is any dirt in there that could make it hard to adjust.

I have a UP-2 and UP-3 on my Euro and they have worked fine so far.

Bob