Sounds like an autolevel failure, it's a fairly common problem but usually just requires a reset and then you're good to go.
When the airbridge is attached to the aircraft an 'autolevel' arm extends from the airbridge, usually with a rubber wheel on the end, which tracks the aircraft's vertical movement as passengers, baggage and fuel are loaded/unloaded and adjusts the airbridge height as required. If the autolevel fails and the aircraft is loaded, there is a possibility that the aircraft door will get ripped off as the airbridge won't move with the aircraft.