Trouble Shooting Document for Apple Remote Management

I have intermittent problem not being able to connect to a macos server. unfortunately, it feels like poking around in the dark. I need to be able to find out why at what step the connection fails. I need logs.

Port 5900 is open, there is no firewall running, and my client is safari vnc://hostname . on one machine, I get the login prompt, on another it just waits forever with a circling “Connecting…” It used to work a year ago, and now it no longer does. Baffling.

Does Apple or someone else have a trouble shooting guide?