Sometimes that just wear and tear. I know alot of the iszui vehicles always round off easy and usually have to be replaced. There just junk. Buy some Napa studs and replace them. I think you will have to remove the hub to replace the studs. In which case I would take it to a shop to have them do this if you don't know what you are doing. Most of the time though its from over torquing the lugs, and or not putting them on right.