Most probably the standard issue with this type of mechanism. The lift mechanism has a small brass pin that seizes in its bushing. Search the forums, I think it was Beogram 1700 in the title of the nice thread that had an explanatory picture as well.
EDIT: it was 1902. Good luck!
BenSA:
Why I had to buy a 6th B&O turntable I'll never know!!
Because five just isn't enough?