no that part works the one hub will not unlock if i take it all apart there is noting in there but the plastic part will not move back far enough to let the splines disengage.
The aluminum ring in the hub is worn... The part the plastic piece rides on. It's been a while since I messed with them but it is a part that you would be able to replace but Ford services the hubs "As a unit" and does not supply internal parts of the hub individually. Had the same problem with my '97 Ramger replaced the hubs with manual Warn hubs at 1/3 the price of ONE hub assembly from Ford.
I thought about having the worn part welded up and machined back down but decided it wasn't worth the trouble.
If you take both hubs apart and compare them (measure) you will find the problem with the side that no longer fully disengages.
You would think the plastic would wear before the aluminum but not so.