Had the above for 5 years and find it invaluable, on average change the batteries in both units each year. Howevr even with new batteries the wireless unit now seems to be malfunctioning....a route that used to be 10 miles now appears to be 5 miles?? in order words the unit seems to be running slow and not recording my correct mileage? Is this a common problem? Should I buy a new unit after 5 years? Is there any way to fix?