From the mists of time ...
I have a clear memory of a portion of a "family" tour of the Kodak processing laboratory in Vancouver my father worked at between 1961 and 1984. It involved a demonstration of the totally manual slide mounting equipment used there.
You have to realize that this was in the heyday of Kodachrome and Ektachrome slides and movies (the Vancouver lab didn't do colour print). They had large, high capacity processing machinery, and during much of the year they were staffed with either two or three shifts (24 hour production!).
The biggest challenge for the slide mounting operators was:
1) boredom;
2) people who would shoot part of a roll, rewind it, reload it, then shoot the rest;
3) boredom;
4) cameras that spaced unevenly or, even worse, erratically, or even worse, erratically, with overlapping frames; and
5) mind-numbing boredom!
They had all sorts of techniques to deal with the boredom - short shifts, frequent breaks, mental tricks to refocus, but every once in a long while they would miss a change in film spacing.
They probably hated astro-photographers too

.
Matt
P.S. my father was in charge of the customer service department, and it was his department that dealt with the myriad of dealers in Western Canada who took in film from customers, sent it to Kodak for processing, and then received it back for customer pickup. So it was he and his staff who got to deal with anyone whose complaints about mounting traveled all the way to Kodak. I expect he too wasn't all that fond of astro-photographers.