FAA is warning Airbus A330 maintenance providers to exercise "extreme caution" around the plane's cargo doors to prevent sudden door movements that can damage the airframe.
The scenario, termed "slamming," can happen when air is trapped in door hydraulic system actuators and lines. If the lines aren't bled before the doors are closed, the doors could drop suddenly. FAA says one reported incident damaged a floor frame, door actuator, and door support frame.
Airbus, which warns of the scenario in the A330 aircraft maintenance manual, issued a service bulletin on the issue in 2005. Read FAA's full SAFO on the issue here (.pdf).