I had seen this when working on a different unit:
371 Forced the camera into the small opening
Worked on it here:
https://www.astrosafari.com/viewtopic.p ... 6&#p586946
Did that repair... still does not work. I am / was going to recheck the Vacuum lines just to be sure.
If that all checks out - then it is on to R & R on the multi-function stalk / switch assy. on the steering column.
There are quite a few good instruction sets for Gen I on the site here.
Finding a proven good one might be tough.