I don't see how the spring would cause run out. There has to be a problem somewhere else. Double check the amount of play the slipper plates have on the top shaft, there should be none, the plates should not be able to wobble on the top shaft. Most likely the slipper plate center bore or the top shaft are out of tolerance. When you tighten everything down any excess play could cause the plates and gear to have the run out you see.