Check the crown and winding mechanism is working and the stem is not broken.

Visually look to see if the crown is in 1 piece and not broken.

Turn it anticlockwise to check it is free and the gasket is not binding

Gently pull the winder into the time set position and move the hands*

If you feel there is a problem, advise your customer. Common problems are immovable crowns glued in place with dirt, broken / rusty stems, crowns that have worn away, faulty "bolt" and rusty setting mechanisms