Door lock problem passenger door Vauxhall Omega?

The electric fob works on all but my front nearside door. It was intermittent until eventually sticking in the locked position. During this period of being intermittent I noticed that it would take multiple attempts to secure all doors with the electronic fob. As I had some time today I removed the door panel etc and found that after some fiddeling with the rods it would work again on the motor (I also gave it a squirt of wd40),, testing it on the fob I got it to work three or four times and then it stuck again. Is there anything I can do to resolve this or is it more expense for a new part?