One of the listings in "Address Book" will have all the info I have input, the other will have only the FAX number. If I make sure the FAX number is included in the one with all details, then delete the one with only the FAX, it will remove the FAX from the other listing. It will also remove the FAX from the contact card under Contacts.
Most all of my contacts were imported from .contact files (Win7), which were imported from .wab files from XP. However, these same issues happen in the same way if I create a new contact using Outlook.
These are actual FAX phone numbers, not eFax email addresses.
Thanks in advance for ideas on this. If there is any more detail which would help to provide, please let me know.