Hmm. Interesting to hear. I bought 2 of these as well, and was wondering why the collars were so hard to snap in. Being new to kegging, I wasn't sure if that's just the way things were, or if it was just because the kegs were new. I haven't actually filled or dispensed yet, since I'm still in the process of putting together all the kegerator bits. I noticed that both posts/disconnects were pretty stiff, to the point where it hurts trying to push down the edge on the collar with my thumbs.
So to adjust the poppet spring, you just disassemble the post, right?