Was the timing adjusted properly ? Also the camshafts pulleys were tightened before the cambelt has been adjusted ? By doing that it puts uneven pressure onto the cambelt and the static timing moves a tiny bit. Due to the low clearance of the valves, the pistons will hit the valves and the rocker arms will shatter first. Good it was found now and not later. I suggest you put a new cambelt and thermostat as well while at it ! If the timing is right there should be no more problems later on if the garrage know and have the locking tools + they worked before on this engine type !