Hello. I've encountered the exact same problem as you describe above and I'm curious to know if you found any solution since these posts were written.
I just bought a second hand Durst Multigraph enlarger (without any user manual) and I have problems getting it to work. Yesterday I opened the head and found that the guide-wheel for the cam that controls the upper filter position was stuck. I cleaned and lubricated it and now it runs fine. I also changed the lightbulb, but it still isn't working properly.
Also, if anybody has any links to any information/manuals on the Multigraph enlarger system I would be really grateful if you shared it.
Christian