I will respond to you over the course of 6 years. There seems to be a problem with the button itself, or with the chronograph mechanism of the movement. In most cases where the button is the problem, it is physically removed or broken, so I feel that the chronograph mechanism is most likely the problem. Either way, it will need an overhaul. Since this is a problem that occurs from time to time, it seems that it can be fixed without regular maintenance by the manufacturer.