Haven't been around long enough on Minecraft to have played the old adventure mode myself, but when I went into adventure mode, I thought it would be just what it is called; "adventure". If you want to break blocks, then play survival. I need something exactly like the old adventure mode for my server so nobody accidentally/purposely trashes my map. Since I am on Vanilla, I can't use plugins unless I mod. I'd rather not do that. Bukkit is awful, and Canary refuses to cooperate. I hope we at least get a compromise on this.
I've had it happen when jumping into a fence or into tight quarters (like in a mine).
I searched multiple times beforehand and that never popped up. :s Sorry, though.
I doubt that carpets caused this issue.