And you made sure that the playback issues and the logged, failing connection attempts are related in any way? Is that you, trying to connect to Roon ARC and failing?
If you don’t use Roon ARC then disable it’s connection to the internet and the failing connection attempts may stop. You can also do this as a test to see if a) none such log messages appear and B) if you still get playback dropouts during the test period with disabled Roon ARC.
If you want to use ARC and have some control over your router you can potentially setup a firewall rule that restricts access to the open port a bit?