I've turned on the AlwaysOn ClsLogger scenario, and what I have observed is that when this happens there is a fairly standard SIP ladder leading to a 403 Forbidden event with the following in ms-client-diagnostics header. If we solve for this one, maybe I will post other issues. The issue that is getting the most attention at the moment is that when you send an IM from a Windows SFB client to a macOS SFB user, an error (intermittently) pops below the message stating: 'This message wasn't sent to Interesting enough, the message IS sent to the user.
We're reaching out to Microsoft Support as well, but wanted to put feelers our here as well and see if anyone has experienced similar. We are currently experiencing issues numerous issues with the macOS Skype for Business client, which is getting to be more and more problematic for us as an organization.