I have seen this raised before a while back, but did not see any solutions. I have just purchased a NN3 Mk 2 and am using a Canon 400D with Sigma 10-20mm. all going well (I still need to learn how to remove Nadir!), but after a couple of weeks the upper arm is slipping down. I cannot tighten enough. Is there a fix for this. I have compared my washers etc. with user guide and all seems in place.

I would be grateful for some help here. I have tried a card washer for the other side of the arm and it works for a while. But surely there should be the correct washers etc. in the Kit?