The two or three plunges I've had apart had a little brass plug between the end of the lock screw and the column. I'm supposing that this maybe grips better and won't damage the column. Possibly that plug needs replacing if yours also has one. It may be possible to tighten the screw that pushes against it and reattach the lever farther around so that the screw travels inward farther too.
to get that plug out you have to remove the base and columns. When you do that you want to make sure the locking lever side is pointed down. Gravity is all that holds that plug in and it falls out easily and has a tendency to roll somewhere you can't find it. Voice of experience on that. The good news is it is fairly cheap. The bad news is that you have to wait for it to be posted to you and the router is useless without it.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.