from reddit:
"Hi everyone, active duty KC-10 Boom Operator with direct information. The aircraft had the boom gimble (attachment point of the boom to the fuselage) replaced a few weeks ago. Two days prior to this incident, a boom operator instructor experienced uncommanded boom inputs. The boom became erratic and hydraulic power was quickly cut and the boom was stowed. MX could not duplicate the issue on the ground, ran some ops checks, and the jet was greened up.
Yesterday, as the jet entered it's orbit, the boom was lowered and immediately became uncontrollable. It was swinging beyond it's roll limitations and eventually ripped from the aircraft, causing a loss of the number 2 hydro system. The crew landed safely."