AirPlay drops out and amplifier Hegel H120 disappears from AirPlay
I have an iMac 5K wired connected (UTP) to my router Cisco RV325. I use Music via AirPlay to play music on my Hegel H120. The Hegel H120 is wired connected (UTP) to an AirPort Express. So no WiFi.
AirPlay stops working, sometimes after 5 minutes, sometimes after an hour or longer. The Hegel H120 is greyed out and can't be reached nor via iMac or iPhone. Changing to Spotify or mconnect same result: H120 has disappeared.
The only thing I can do is to shutdown the Hegel H120 and interrupt the power cord. When the Hegel H120 reboots it works fine, but the problem reappears randomly.
My HiFi dealer and I thought it was the Hegel H120 but even his amp which I can borrow has the same problem!
I have checked everything (firmware, reboot router and AirPorts, changed cables, tried with fixed IP or dynamic IP, ...) but nothing helps.
Is there a known issue in Music/AirPlay/... ? What can I do? At the moment my HiFi set isn't fully functional and we have no clue why.
AirPlay says: