@markrb
What's happening is that your SR9c does have a Mag DC and you're actually releasing the Striker into the disconnect. Hope you haven't done it too many times, you might have caused some damage to the Striker or Mag DC. Take a look
here at my video how-to on removing the Mag DC. It's on my SR9, but the steps are just the same for the 9c. If you want more detail, click the how-to link in my signature for my text/photo how-to.
Remove your Mag DC and inspect both the Striker and Mag DC for damage. You might not have done any harm, especially if you only did it a few times. If nothing looks marred, it should be fine. If you were planning on removing the Mag DC, I'd leave it out and reassemble. If you weren't, put them back in and only dry fire it with a mag in place. If you see damage on either part, call Ruger and get a replacement for the part that was damaged, or both if you're not sure of any damage. If the Striker is damaged any and even without the Mag DC installed afterwards, it can still cause malfunctions. Rather be safe than sorry.
Josh