This is more to help others that may have this issue.
I have 3 machines on Fast Track builds. Today my laptop kept reverting back to the previous build before completing the update. After the 3rd attempt I poured through the Event Viewer logs and discovered an error trying to obtain a device drive for the Wireless Keyboard Filter. So I unplugged my Microsoft wireless mouse and Transceiver for the 4th attempt. This finally allowed for the upgrade to be completed successfully and after everything had updated I plugged the Transceiver back in with no problems.