I was able to connect my Macbook Air early 2014 (High Sierra) to a Fireface 800, using a Thunderbolt to Firewire Apple adapter. After installing the necessary drivers & the Flash update tool, I was able to test that everything was working by simply using iTunes.

This worked for about 2 minutes then the connection was lost. After that, trying to restart, reinstall the drivers, Disk First Aid nothing worked. Launching the Flash Update tool gets the No driver or device found error.

The Fireface 800 has two green leds (In, Out levels) & the Host red led lit. The Thunderbold to Firewire adapter feels a bit warm for only two minutes of play.

Has anyone experienced a similar behavior?