This a common problem with auto and manual locking hubs .the main cause is dirt and crud getting in the hub /via bad o-ring seals.

also if you do alot of forging of streams or run in the sand all the time its a common maitenance practice to clean them regularly.

What happens is they stick and wear out the front
spindle bearings and the axle shaft bearings and also wear the spyder gears in the front diff..

I wouldn't expect Ford to help with the bill unless
your still under warranty

Rich