The lock cylinders are interchangeable. It's the lever that is clipped on that is not. The 77-78's do not have the rods, so are easier to clean up, and no adjustments are needed. I'd try pushing the lock button down and see where it's binding. Also try locking and unlocking with the key. I'd think you'd be able to see if anything is binding up. It definitely looks like everything in there needs a good cleaning & lubing.
Not sure if this applies to your Z, but on the 77-78's, its the lever that is clipped on the lock cylinder that usually wears out. There is a cam lobe on the lever. That lobe wears down to the point where it might not catch to lock or unlock. On your setup, one of those rods is probably binding up or slightly bent. I'd play around with it since you have access now.