Does anyone have the quirk of the hour register on the chronograph sticking when resetting?

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If I leave the chronograph running on my el primero 03.2040.400 for a few hours then stop it and reset it. The hour register doesn’t fully reset back to zero hours.
If I then push the reset push in harder only then will it reset.
Is this a quirk of the movement or something more sinister?
The watch has just been serviced
If anyone can shed some light on my question I’d greatly appreciate it.
Best regards