Thanks, Mike.
Here are the details:
The issue earlier today was that the M32 seemed to be trying to play multiple songs at the same time - or rather, the display was flashing rapidly between previous songs and current song. The actual song being played was okay. Then stuttering began (within 10 minutes of the flashing). Then the card locked up. (Behaved like an out-of-memory situation, or too many processes running, if I had to guess.)
I rebooted the BluOS card. No go. I rebooted the Roon core. Fixed it - and it worked for a while. Then after about 30 minutes, the same behavior as before returned. Note that everything continued to work fine with the native BluOS app. Likewise, the Roon Core seemed to also be functioning fine with a PS Audio DirectStream DAC, so I switched to that, and used it for the rest of the day (without rebooting the Roon Core).
I am running Roon 1.2 (build 165). Core is running on Linux 16.04.1 LTS Server (no GUI), which is up to date. Machine is an i7, 8GB memory, 64GB drive (no music files). Files are stored on a NAS (WD PR4100) - about 2000 albums.
Controllers are running on macOS 10.12.3 (Mac Pro 2013) and iOS 10.2.1 (iPad mini 2).
Outputs are a PS Audio DirectStream DAC, the M32/BluOS, and an AppleTV (via Airplay). No stuttering or any other problems with the other devices.
All components are wired ethernet. Router is Apple Time Capsule (newer vertical model). Switches are NetGear (unmanaged) + HP (managed). Media is a mix of DSD64, 24+16 bit PCM (ALAC). Original problem did not seem to be related to the media type.
A little while ago, I rebooted the Roon Core a second time, and the missing M32/BluOS reappeared (as it had before reappeared upon Core reboot), and so far the issue described above has not reappeared.
I originally assumed the problem was with the BluOS card, but now I am thinking it might be the interaction between the card and Roon Core - especially because the Core is running on Linux. Maybe the combination of the “Uncertified” BluOS + the Linux Core? Next time, if the problem occurs again, I will reboot only the Core, to see if that temporarily fixes the issue.
Again, without rebooting the Core, I could use Roon fine with the PS Audio DAC. But the M32 was not being found. Rebooting the Core was the only way to get it to “see” the M32 again.
Hope this is helpful.