It doesn't look like this was the particular problem that caused your failure but the style clamp on those Bontrager seatposts doesn't seem well suited for carbon railed saddles. I had that exact same saddle/seatpost combo briefly and was pretty concerned with the minimal/side points of contact and the amount you have to torque the seat clamp to keep everything tight.

I'd suggest a metal railed saddle or swapping the seatpost for a more traditional clamp design if you stick with carbon rails.