I have noticed that the connex links have to be installed int he
correct orientation or they do cause some skipping. Predominantly on
the smaller cogs, 11t-13t's.. Larger ones didn't seem to affect it. I
mistakenly did one wrong on my own bike and it was painfully obvious in
the stand that it just didn't fly, so I flipped it, and life was good.
There is anotherh problem with them, but it is mostly on the shimano
ones.. They seem to have a propensity to break.. a run of chains with
weakend/weak side plates got made, and the link pins pull through. not
cool. warranty them out though..