I am not sure what the term "Robby cut" means, however if it means Main Rotor to Tailcone contact that has severed the Tailcone, then this is usually consistent with "Low RPM Rotor Stall"
Low 'G' mast bumping can cause a failure of the main rotor drive shaft, which allows the rotor hub and blade Assy to part from the aircraft, complete with a part of the drive shaft.