Hi sorry for your update troubles.
I tried the same update this morning an it succeeded without a glitch.
I followed the link in your post and seeing all the troubles people have setting this up makes me think docker on unraid Is a bit more difficult to set up 
Anyway, your logs over there are full of permission errors which make me think there are wonky things going on with permissions. Does unraid something special with userids running the container or with file permissions or fs attributes? Did previous updates work fine? (In that case no clue why this particular one failed, maybe the Roon guys changed something in the update process which in turn unveiled some underlying problem ?)
Also, same update in vanilla VM worked fine you say; this enforces my suspicion above.
Finally, you state over there that VM runs more smoothly. Is the drive mapping topology different from the docker setup? At least for the docker version mount /app and /data on SSD, /music and /backup can be hosted on rotating hardware.