Help with Beseler Dichro 45 / Filter Lever doesn't stay rearwards

Hi, how can I repair the filter lever? It doesn't stay rearwards, therefore, the light is not going on... Any suggestion? Thanks!

Any luck? I've never come across a parts diagram for any Beseler head. I had a quick look inside mine. Not much to see, most of the mechanism is hidden under the lamp housing. I can see a spring move on the right when the lever is moved. On the left under the filters there is an arm that raises the filters. There a couple set screws that hold it to the shaft that runs under the lamp. Maybe they have come loose.

George