The same thing happened to me about a year or two ago. I bought an earlier (SN 8**) R9S off a forum member and I noticed a small crack at the rear on my second outing. If I recall correctly, there was a small batch of slides several years ago that were more prone to cracking. Even though I was the second owner, they replaced my slide for free. Don't worry, just give Maria a call and let her know. They're good people and will take care of you.