I recently picked up a Kollmorgen K-222 autocollimator from an auction. The horizontal axis adjustment appears to work properly. The vertical axis adjustment is stuck. My first guess was the instrument had reached a travel stop. However, looking through the eyepiece, it appears it's only 25% through the full travel--neither at one stop or the other. Even after taking off the adjustment dial, I cannot turn the screw. I use autocollimators frequently but I've never had to do repairs on one. It's a beautiful piece of optical engineering, but there seems to be no support for this instrument. I'm concerned about turning this problem in to a real can of worms making some foolish attempt at repair. Any thoughts on what's going on here and what to do about it?