[Brockmeister]

Hi Folks. I just came back from my local tire distributor. My box has been vibrating lately at high speed, so I took it in to be re-balanced and have the wheels aligned. Shop called me and said that 3 of the wheels lined up but the right rear was still 1/2 degree out after adjusting the eccentric as far as it would go.
any ideas as to what would cause this? And if so, any ideas on how to fix this?