It sounds like to me the only thing that could be wrong is that the Magenta dichroic filter or all the filters are stuck in place completely in the lights path.
This would be due to the head possibly getting banged when moving or the gears are meshed.
As someone pointed out , most colour enlargers have a white light point position and if you cannot see bright light and complete filtered light then you have a problem.
Also the other source could be within the mixing box where one of the side panels has fallen and is blocking the light path. This has happened as well as the dichroics locking in place.
A camera store probably would not know how to look for these problems btw.