Thanks for all the information you’ve shared and for your patience while we got a moment to reply.
Based on all the symptoms you’ve described, it is very likely that you are affected by a known bug:
What might also interfere is the fact that the device you’re using as a Core (the Synology NAS) does not meet our recommendations for an optimal experience. Would you be able to try to use your Macbook as a Roon Core and see if the issue persists