Stuart,
How far off were the CD's not returning them to the original inserted position?
Maybe replacement of the mechanism means that the CD memory / position function was wiped clean and you need to restart to set the position again? could that be a possibility?
I have my BS9K since 2001, and have never needed it to be serviced, although maybe it's time for mine. The CDs all return to their positions, but they may be slightly off kilter... I don't mind, though.
Have you tried to store a position, and seeing if that works? If so, then definitely the service caused the memory to be lost. Maybe it's inbuilt memory in the carriage?
Please keep us posted.
-Sal
Love B&O, but no longer addicted.