When Voyager failed last year with a CMOS memory error, one of the big problems was that a bunch of low level information was gone or conflicting. For example, they sometimes had to guess assembler instructions because the code printouts were low quality photocopied pages. Or because there were handwritten comments or comments scratched out with pencil without any clue about why it was done.

One saving grace was the fact that the architecture and the code space was simple enough so that they could reason through the symptoms and actions to take, something that would have been much harder with modern spacecraft.

Check out this amazing talk: https://youtu.be/dF_9YcehCZo?si=W_b3NJ7vgxaYS1__