Well , they will surely know where the mechanical issue is by now, there is a chance it may have been operator error, as unlike modern bridges where it is just press a button , these old bridges must require a sequence of operations to be carried out correctly, so one missed step or out of sequence step would cause issues, but then my bet is on a mechanical failure, something a simple as a sensor failure can easily stop these things, the sensors would probably not have been an original feature and may have been added at a later date to reduce the required manning levels , ie light to say when something had happened that would have originally been eyeballed by one of the bridge crew.