What a shame. I'd start by looking at the cannon pinion tightness where it fits to the centre wheel.
Say it's a 550 series automatic three hander with a central sweep second hand, then the train is running as the second hand works. That means the centre wheel on the rear of the movement is turning as it is part of the train. It protrudes through the plate of the watch to the dial side and the cannon pinion is a press fit on there. If it's loose, then it won't be turning and the minute hand is mounted on here plus it drives the hour wheel where the hour hand is mounted (via the minute wheel). You can usually tell as the crown movement feels very loose when setting the time.
Hope this helps a little, Chris
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