You don't specify which Lee trimmer you are using, but if it is the Quick Trim (either powered or hand cranked) you probably just need to remove the spacer ring. It is a free-spinning knurled ring below the black adjustment ring, and Lee says to ADD it for cases longer then 1.25". Well, it comes with the ring already installed so the instructions should say to REMOVE it for cases shorter than 1.25", which would include the 9mm Luger. Removing the spacer will also give you access to the aforementioned ball. Simply grasp the shaft above the cutters in one hand and twist the top portion (above the adjustment ring) with the other. If you have the powered version this will be where you attach the drill. If you have the hand crank version, grab the crank itself. If it won't unscrew you might want to wear a leather glove in the hand holding the shaft, but trust me, it does screw off. That should fix your problem. I just tried installing the spacer ring on mine, just to see, and it behaved exactly as you described.
I don't think removing the ball is appropriate in this case, since Lee says that is for when the case neck is too small for the die. Oh yeah, and the cases should be resized before trimming or they could be a tight fit into the die.
