I'm coming into the conversation a little late, so I apologize for that (took a few days off for spring break with the kids!). I'm sorry you're having issue with the split rings you purchased from us. As many here have already suggested, there's definitely some technique to putting these together. I've built more than I can count, and I still semi-regularly end up with sprung split rings. A couple of suggestions that haven't already been covered:
Consider using narrow opening split ring pliers. These are widely available online, including from us, many of our competitors, and from Amazon. The lower jaw on these pliers extends past the downward point of the upper jaw (think underbite), making it far more difficult to overextend your split rings. Basically, they limit how far you can open your split rings. I use these almost exclusively when building chatterbaits.
When I'm building these, I use two pairs of split ring pliers (or, depending on what I have on hand, a pair of split ring pliers and a small pair of round nose pliers). The technique is difficult to describe, but, basically, I use the narrow opening split ring pliers to get the ring started on the blade, then, while using the narrow opening pliers to keep the split ring open, I'll use the other pair of pliers to rotate the split ring onto the blade. Not sure that makes sense, but I've found it far easier to maneuver/rotate the ring/blade this way without overextending the ring. Maybe I'm just losing dexterity as I age!
If you like, PM me your order info (order number and/or email address) and I'll double check to make sure we sent you the right rings. It's possible another style of split ring slipped in there (stainless steel would be a nightmare on these). We'll do what we can to make things right.
Thanks, and good fishing!