I cannot connect to either Roon Core

Roon Core Machine

I have both a Nucleus + connected to my main music system and a Mac Mini with another Roon Core connected in my home office (2 lifetime licenses).

Networking Gear & Setup Details

My network gear is Unifi, with a Killer E2400 Gigabit Ethernet controller.

Connected Audio Devices

The Nucleus + is connected via ethernet. One DAC is an exaSound e32, connected to an exaSound Sigma Streamer. These two are interconnected via USB. The exaSound Sigma Streamer is connected via ethernet to the Nucleus +. The other DAC is a MSB Premier connected via ethernet to the Nucleus +.
The Mac Mini is connected directly to a Schiit Bifrost via USB.

Number of Tracks in Library

My library is 72,000 tracks

Description of Issue

Last night the Nucleus stopped working in the middle of a listening session. I could not see either Core with the Roon app. Since then I restarted the Core in the Nucleus +. Reconnected to the NAS, restarted from a backup and this system seems to be back on line. I have not yet tried reloading the Core in the Mac Mini.

The Nucleus stopped working again right a way. I have tried rebooting, powering off, then on via the power button.

When I restart the Nucleus +, Roon Server Software does not restart. When I restart the software manually, it only runs for a few seconds then stops. The Operating System is Version 1.0 (build 227), Server Software is Version 1.8 (build 931), Roon Labs Software is Version 1.0 (build 12).

Fill in the rest of the required information.
If you can’t see either core and presuming that you have more than one control device, it loks liie a network issue