I just remembered something else that might be helpful. When I first got my d8b's, both didn't have a clock card in them.
So, I found a used one, but when it arrived and I pulled it out of the anti-static bag, right at that moment, one component fell off of the card. Maybe an old cold solder spot or something.
When I tried to fix it, and just gently handled the clock card, another one of the same types of components fell off of the card as well (...and I was screaming expletives by then). I'm wondering if that was something of a production issue, that could affect other such cards as well(?)
I'm attaching a picture here. The annotations are from what I wrote back to the person I bought the card from (we both speak German), and it just says that the top one fell off first, and the lower one fell off while soldering...
The card worked, after I soldered both back on, though.
Anyway... maybe you want to check if your sync card still has these components on it, and if one's missing, try to shake it out of your desk, hahaha
I know it would be a coincidence if it was the same issue, but you never know.
Again, good luck!