I have the same problem and was told just to leave it in place as even if you get the plastic screw out, you'll never get another one in.
My problem was that the pressure was too much for the cam so the cam couldn't rotate. I ended up pulling the cam out of the top with some pliers, gently fileing the edges of the cam so it could go back in the hole, and cutting the spring slightly to shorten the length, now I have no problems with my rudders.