I have had this Junghans watch for some time and now in need of a service before I go ahead can I ask the watch always has run lovley but now it is losing some hours a day,can I ask why the watch is still running but the hands run slow or stop even that the air Spring is going fine hand second hand also goes round fine,can I ask what could be the fault to look for before I strip it down.hope some one can help me thank you.