The Latest Studio Scorecard
The RayDAT card turns out to be fine. The source that was feeding ADAT 3 and ADAT 4 isn't. This means that either:
The Frontier Apache patch bay has a bad channel (unlikely)
The long optical cable connecting the patch bay to the d8b is bad (quite possible)
The OPT-8 card in the d8b has gone bad (possible -- I have a spare)
Something else internal to the d8b has gone bad (I hope to heck not!)
Something is not plugged in correctly (always possible)
More diagnosis is scheduled for a later date.