There's a big clue. HD audio.
HD audio has a PROTECTED PATH in it. This is something of a well discussed area. My quick fix is to use a Y audio cable to loop it back to the aux input but sometimes that fails because HD audio is again "a protected path."
Microsoft had to protect HD content. It's a long story but those that never read about this may think the PC is defective or broke.
There's lot more out there about it.
Sorry, my only workaround has been to record it with an analog system and merge it back later.