WHAT IF.... the hubs just need some TLC. I think this is what needs to be done.
The inner race of the bearing is held in place by a stop on the inner part of the axle and the retaining nut on the outside.
Try this...
(1) Loosen the outer nut on the axle.
(2) Take up any slack with the inner nut. It should be snug against the inner race this will hold the inner race tight between the stop on the back of the axle and the inner retaining nut.
(3) Retighten the outer nut on the axle.
(4) Check to make sure the hub still spins freely repeat for the other side.
I don't think the bearing has gone bad. I think there is some play between the axle and the inner race of the bearing. It you remove the play the bearing will function properly.
I think it is worth a shot at adjustment before buying replacment parts.
All the Best
Tony