NSM Prestige fails to play both sides of record

My NSM Prestige 160 plays the A side of records properly, but when I select a B side the machine selects the correct record from the carriage but plays the A side backwards. I am therefore assuming it recognises that a B side has been selected but the arm is not moving to the correct side of tge record.
Can anyone advise where the problem may be and how to correct it? (I have the service manual and a fair degree of technical ability). Thank you.

A - B Seitenumschaltung auf der Rückseite des Laufwerks verharzt .

Hello,

this problem appears frequently:
[forum.jukebox-world.de]

Regards
Jens

Eigentlich gehört der von Jens verlinkte Beitrag ins ??? Archiv , so wie er ist zu Punkt 12 .