I know this is an old thread but did you look at the battery connection tabs to see if they are rusted or corroded from battery leakage? I had to use very fine sand paper to clean them off and then when I was done with that I rotated the batteries while seated and everything works fine. If it's old some craft shops carry the mechanism that controls the clock and the face of the clock can be unscrewed form the back along with the battery box. Hope this helps out.
Macgerailt
January 2014