This issue is apparently caused by a mismatch in the build versions between the Remote and the Core.
You need to get all your Remotes and the Core to the same (and latest) build. See this post:
From your report, it looks as though your Core on the iMac is still at an earlier build, and needs to be updated to build 1211.
If you can’t get the Core on your iMac updated by going to Settings > About using the iMac itself, then you will need to follow these steps, as long as you have backups:
- Find the folder that says “Roon” Mac software location
- Rename the “Roon” folder to “Roon_old”
- Reinstall the Roon App from our Downloads Page to generate a new Roon folder
- Verify if the issue persists on a fresh database before restoring the backup