Tire wear outside rear curb side

Had this problem in January, Took it to Camping World of Chicago. They replaced the shackles and bushings aligned the axles. I replace all 4 tires and rims had them balanced. Drove to Florida after it was in the shop a month.Looked OK Drove to Nebraska almost 3700 miles for the trip and i'm back to square 1. I have a warranty but I would like to get a little more insite on what might be wrong. Trailer is not over loaded. Trying to find a Dealer to make the proper repairs in this pandemic time.