The handle pulls on a cable in the lock mechanism to release the catch, it could be getting caught in the mechanism. Personally, I would take the lock out (there's a small torx screw holding it in on the door edge, loosen the screw and wobble the lock til it comes out, dont unscrew all the way, its not necessary!), release and remove the handle and get at the lock mech with spray grease, not WD40 as that stuff isn't good enough.