The dichroic color heads use a single filter of each color which is mechanically imposed on the white light, the lever moves all the filters out of the way and then back to the previous settings when you are ready to print.b It sounds like something is binding, perhaps the head was dropped or damaged before you acquired it or the lubricants have dried out. Fixing one is a DIY project, I did it just once, and swore I would never take another color head apart! With the lamp off and the head unplugged you can take off the covers and watch how things move after removing a couple of covers. Good luck. You might also contact Beseler, or visit their website for an exploded diagram of the head.