It's possible that you have a bent axle between the perch mount and the spindle or spindles on the side where you're seeing the wear. Usually on the passenger side, and it's easy to do if you turn too sharp and the wheels hit a curb.
The axle tube under the RV isn't bent, but it may be bent from the spring perch to the spindle end.
So, one side is fine, the other side is whacked. It may be time to replace the suspension due to wear. The factory components usually have a very short life and need to be upgraded to grease-able parts for long life.