Windows Live Mail randomly losing contacts

Computer: HP Pavilion Desktop

Operating System: Windows 8.1

Problem: Over the last week, contacts have been getting randomly removed from WLM. We had approx. 650 contacts and are now down to 617.

Troubleshooting:

1. Scanned the computer for infections (MalwareBytes, AVG) which came back clean.
2. Checked for Updates, which are current.
3. Reviews the Event Logs, nothing out of the ordinary.
4. Performed a backup of the contacts.

Thank you for your help.