If your Roadster interior handle stops opening the door but you can still feel that the cable is attached
you are suffering from a very normal problem. It's not the cable or the lock but the handle itself.

Remove the exterior door panel

Feel through the weather shield in the area marked below. You should feel the raise bump of a Torx15 screw head. 



Push the Torx 15 screwdriver through the weather shield and loosen the screw. Don't drop it inside the door.



With that screw out, the interior door handle will be free to pull out of the door card.



Flip the handle over to reveal the problem.

The hingle pin of the cable pulling mechanism moves up out of position. So when you pull the handle to
open the door, the tension of the cable causes the mechanism to twist instead of pull fully.



It only affects the pull of the cable by a few millimeters but it's enough to stop the door latch from opening.

Fixes

It goes without saying that the pin should be pushed back into position.
Some people have this problem so regularly that they have learnt to push a screwdriver in between the handle
and the door card and push the pin back into position. Great if you want to damage the door card over time.

Instead of continually fixing it, just fix it correctly 1 time.

Push the pin in position, rough up the plastic around the area and apply some 2 part epoxy in the directly the
pin would travel. This adhesive will set hard and act as a barrier so the pin no longer slides out of position.

Weatherproofing

Since you have made a hole in the weather shield, you will need to reseal it.
The easiest way is to use a small strip of duct tape.



Check everything works and put everything back together.