VW bike rack lock issue

[Steve O]

Hi

I’ve just unlocked the locking knobs on my VW rack and two of them won’t engage or turn to open/close the jaws.

When locked again they all spin freely as they should so it feels like something has seized up or rusted internally over the winter.

anyone had a similar issue and resolved ?

or ideas on how to sort without resorting to breaking them off if possible?

thanks in advance.