Wow sorry to hear about your troubles.. I read the reviews on the Play Store and they were not good at all. The app has a 2.1 rating. Many of the posted reviews claim the same issue with accuracy errors that you experienced. I don't think there is much you can do to fix it but reach out to LaCrosse and let them you are not happy.
A temporary solution could be to publish your data to Weather Underground and then use the Weather Underground app to view your station. I read that it was possible with the V40 to upload to WU.