Not the OP but the crane incident was shortly after the first incident. The higher ups wanted to use the polar crane to lift a bunch of radioactive debris out of the core that almost melted down. At least one of the workers (Rick Parks) ended up whistleblowing over it because the crane was the same one that was there during the incident and most likely had taken damage. He was concerned the crane would fail while lifting the radioactive debris out (around 1000 lbs of it) and fall back onto the core. Check out the Netflix document Meltdown: Three mile Island for more info.