Does it looks like this when you try to set the time?
Common failure on this movement, and any others that have the hour hand that jumps in 1 hour increments. It's the hour wheel that has failed:
As you can see it's 2 wheels in one, and the mechanism that keeps the 2 wheels coupled to each other eventually fails.
I replace these automatically on every watch I service with this style of hour wheel. He will need to ensure that he orders the right height for this wheel - there are several different heights depending on the specific model that the movement is used in. For example the black GMT will use a shorter version that the white GMT (Great White) will.
Cheers, Al
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