From your photo the spindle doesn’t look bad.
When you say reluctant tonearm assembly what do you mean?
How old is the servo belt and did you get a proper one from Beoparts?
A worn or incorrect belt is the source of a lot of problems.
If you have an arm assembly that moves a short way then seems to hang up (and the belt is not the problem) then it is likely a problem with the electronics controlling the servo.
Old capacitors, bad connection somewhere and, sometimes, faulty photo sensors.
There are also two adjustments on the control button panel for the left and right scan control. The service manual specifies what the steady-state voltages need to be for those two controls. If they are not correct they will cause problems with the arm assembly movement. If you dive deeper into the related threads I linked to there should be some posts about those scanning sensors.
If the BG8002 is still operating on original electronic parts then circuits could be trying to operate with out of tolerance components (like electrolytic capacitors that are no longer in spec).
-sonavor