Are you familiar with a net video of a Sea Knight dropping off into the fantail during landing. It apears to be a rotor stall (From my fixed-wing point of view), but it might be an example of 80-400? rule violation in a twin rotor. The aircraft was descending to land on a helo pad of a moving ship when it pitched up and rolled to IT'S right violently. As if the ascending side of the rear rotor disc failed.
I'll see If I can find a link.