Yeah, that is actually I was curious about... sorry that you too have troubles with those o-rings - but in the mean time I do feel a little bit relived... I was thinking that the problem is from my part... And yes, those o-rings not just simply fall out of their place, but they're really jumping!
I have several types/generations of EK blocks and SLI-connectors, but this Terminal series is terrible to install!
This week I already flooded my system twice because of that stupid connector... kinda getting boring to take all thing apart dry it then put it back together...