"Low Success Rate of Active Name Resolution" NNR Warning, But Requirements Are Met

Question

We're seeing the above Network Name Resolution (NNR) warning in the Defender for Identity Health Status page on the portal (screenshot below). We've ensured that the firewall requirements are met and that we fulfil the other recommended configuration steps. We've even conducted network tests that, so far, indicate that no referenced TCP or UDP connections are being blocked between sensor on server and target host. We have a call logged to Microsoft Premier Support and, after a month, have made no progress towards a resolution. Frankly, they are dragging their heels and I'm at the point now where I see a clear possibility that it may not be resolved. As Defender for Identity is critical for us and we are strict about cybersecurity, I've decided to resort to this community for assistance.

Can anyone tell me how I might go about troubleshooting this further? My Windows Firewall tests produce log entries showing connections being ALLOWed.