I'd assume there's a gear that has a slight bend, or burr on it. Or, something is touching the front (minute hand) or back of the dial's stick rivets (5-minute intervals). A qualified watchmaker should easily be able to spot the problem.
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TT OysterQuartz, SS/Black "U" Daytona, TT GMT II-C, DD OysterQuartz, Breitling Aerospace, Omega Speedmaster Pro
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