micromega critical focuser - lens head loose

Hi, the lens head is loose on the swivel - when I adjust it pararell to the mirror it falls down under its weight. I tried to tighten the screw by hand (I don’t have this special tool) but no improvement. Also I noticed that there is only one washer near the tightening screw, while there are two of them other side - is it possible that I need two of them both sides?

-) all photos of that device I found on the net showed 2 washers outside vs. 1 washer inside (or least one gets the impression of there being 2 washers)
-) you will need such special (spanner) tool some day for a camera lens anyway