The quality of the shouldered lug nuts for Weld style wheels is down these days. Maybe now would be a good time to upgrade to 5/8" screw in studs and the flat flanged style lug nuts, since you already have it apart.
Yes, it's definitely the lug nuts that are stripping, but then you have to break off the stud to get it off the axle. I already have Moser screw in studs, 1/2". I just need to find some better quality lug nuts that work with Weld draglites.