Accuracy *should* be at least very good, if not absolute, certainly much better than what you are getting.

Many different types of rangefinder adjustments exist.
Some have separate (though interacting) adjustments for infinity and close range.
Unfortunately I've never opened the E-M Bessa up (I'm very slowly restoring it, fine adjustments are still way in the future).

Try:
http://www.kyphoto.com/cgi-bin/forum/discus.cgi
Lots of very competent repair people there