Cantilever parasol?

my cantilever parasol, when opened fully has a bit with a sort of cup on it that when fully extended connects with the underside of the parasol and locks into place holding it in place. this is now not happening. It fully opens, the cup part locates but as soon as i let go of the crank handle it pops out and the parasol is still open but no longer taut
Rachael, July 2021