How to fix a dual flush toilet cistern cable?

Hi,
I have a dual flush toilet cistern. When the push button is operated it stay down and does not come up. Because of this, the flush valve that goes up and down within the cistern to let water into the toilet bowl stays up so water keeps going into the toilet bowl. I am nearly sure that the problem is with the cable that connects the push button to the base of the flushing valve. The cable is slightly bent and will not "push" the flushing valve back to the closed position unless I do it manually. Any suggestions on how to fix this ? Does the cable have to be replaced ?