I see similar messages in /var/log/messages for dmapd; I don't think they are anything to worry about.
You might try this to see if it improves dmapd performance:
1. Login to your VB.
2. Stop dmapd:
3. Create a cache directory for dmapd:
systemctl stop dmapd.service
4. Start dmapd:
mkdir -p /var/db/dmapd/DAAP
5. dmapd will start and will cache database info in /var/db/dmapd/DAAP/. This could take a while depending on the size of your music library in /storage/music/flac. When this completes, VortexBox will show up in the iTunes SHARED sidebar.
systemctl start dmapd.service
6. The initial load of songs into iTunes from VortexBox takes some time, but subsequent switching back to VortexBox from other iTunes sections is very fast.