Just remember the shift on the fly needs some wheel spin to engage properly after turning the switch. You can not first get stuck, turn the switch and think you will be in 4x4.
Here is also a good link for maintenance for the esof hubs and many other things.
http://www.guzzle7pt3.com/index.php

The usual culprit of the defrost mode is the loss of vacuum. Most of the time the vacuum tube is broken at the back of the hub. Turn the wheel all the way one way and look back there at the hoses. They are near the brake lines. Another quick test to see if you are locked in or unlocked would be to reach around the tire and see if you can spin the axle shaft at the wheel nuckle. It will not spin if the hub is still engaged.

Welcome to the FTE family to all the new guys!