the audio is gone

[arjepsen]

I wonder if it could be a clock-related problem?

[Phil.c]

It sounds (excuse the pun) like a clock issue, have you tried a card clean and re-seat, another clock card, the original would do, clock set to internal, also, when you did a ribbon connector re-seat, did you do the ones that are slightly hidden, there are others totally hidden but boards have to be removed to get to them. I had a different issue to you where a re-seat didn't work until I removed a couple of boards to get to the hidden connectors, it worked after that, in your case, a lot of work doing this and no guarantees.

I would concentrate on the clocking first.

Do all the inputs fail?

Has the sample rate changed?