was oil starvation, if it is , it will be easy to spot because the rocker arm will be galled to the rocker shaft.. I've seen it before on other cars. However if the rocker can rotate and isn't seized to the shaft then how could oil starvation cause it to break where it did... If the bulletin i posted doesn't apply or has already been done, then it looks to me like valve float, meaning that the rpm was actually a ways south of 5k and the valves floated, When this happens i've seen it break both rockers on the same cylinder quite frequently.. along with bending valves and touching pistons.... Now if its valve float then i would definitely replace the springs when you replace the rockers and whatever bent valves you have. All the springs. John you may not have seen this before cuz desmos can't float the valves