I have an Astro that will run great and keep perfect time for several days then, out of the blue, the hands stop turning. At first I thought it must have been the hack spring adjustment, so I readjusted and after 7 or 8 days it did it again. Each time it stops, the watch is humming away like nothing is wrong. Only thing I can think of now is that it must have a bad index wheel. Any other thoughts?