Yep. This doesnt say anything really about the quality of the rifle.... since it functioned fine for the factory test firing, and functioned fine for the first 16 rounds for you, I would venture it
a. Was like that from the first assembly, but since it ran fine for test firing and your first 16 rounds.... it went undetected. No fault.... other than poor assembly or bad ring.
b. Failed like that on your 16th round, and all subsequent rounds failed. That is a ring failure. Bad ring, or damaged while it was installed.
Bottom line - things that are going to break, will typically break when something is new. Find any potential issues, remediate them, and you have a fine rifle.
I would be a little miffed if RRA acted like it was my fault, and it could not have left the factory that way. Of course it could have, RRA is not perfect. Nobody is.