R90 selects wrong record choice

[stingman]

 I continue to have an ongoing problem: when I select a record, one or two records after my selection is chosen.
I also have a RB8 bubbler with the same Rowe Ami innards; this unit works perfectly.
All optical switch and pot adjustments on the R90 have been made over and over with the same result; no joy.
The motor has been lubed and has no play in the bearing shaft, the sprag wheel has been renewed with new bushings.
My latest effort was to swap the optical switches and mech computers from one juke to the other. The parts from the R90 installed in the bubbler worked fine, while the  ones from the bubbler resulted in the same incorrect selection problem with the R90, even after making new adjustments.
Having eliminated these items as possible suspects, my next choice would be to swap out the whole sprag assembly from one juke to the other. This I am not likely to do for fear of creating unforced problems with the bubbler; one problem jukebox is enough.
Based on the process of elimination, only the sprag solenoid or the detent mechanism remains suspect. Is it possible that something in the sprag assembly is at fault and causing it to overshoot the correct stop?
How do I isolate this problem to a failed part or adjustment?

Stingman