If there was a "short" as you say the battery would supply an almost infinite current and get very hot and become instantly flattened.
It is more probable - from what you say - that the problem is one of an open circuit - i.e. contact is being lost and current stops flowing - the heart stops beating.
There are not many specialist repairers of electric watches - here's a link to one in the UK
http://electric-watches.co.uk/repairs.php
Good luck...
Peccavi
April 2013