Wanted to lock my manual hubs for 4 wheel operation but they failed to lock....front drive shaft was rotating. After moving the hub switch back and forth it finally engaged. Is there anything I can do to prevent this from happening and is this a sign that they need to be replaced.

 

Time to clean and re-grease.
I like using full synthetic greases as they do not thicken up as much at low temperatures.

 

Over time the dial can seize fast and refuse to budge. Try lubricating them as said before and go from there. The nice thing about manual hubs over the ESOF hubs is the price. A set of Warn replacement hubs is less than the price of one OE ESOF hub.