hAP with CAPsMAN and Airplay 2 - Cannot connect via Airplay 2

Hello,

I opened this thread because Airplay 2 seems to work different than the older Airplay (1).
I am using a Apple TV 4k, a Yamaha receiver with the old Airplay (1) standard and the mobile devices in the same VLAN. Every device has an IP adress of this VLAN, all devices are at the same subnet.
If I try to stream some audio to the Yamaha Airplay works. If I try to stream audio or video to the Apple 4k via Airplay, the iPhone cannot connect via Airplay to the Apple TV.

I configured Airplay 2 at the Apple TV like mentioned in the manual. The Apple TV has been added to a room in the Home App and I can see it in this app at my iPhone.
Everything else works at the Apple TV and the other devices. All devices are connected to the internet and I can stream via apps at the Apple TV.

Does anyone know what works different at Airplay 2 or what do I have to configure different at my mikrotik devices?
My network consist of a Routerboard which is handling the whole network and is the master of CAPsMAN. It is configuring all hAPs. All hAPs are working fine, I get WLAN at every hAP. The Apple TV is connected via ethernet cable to the same hAP like the Yamaha. My iPhone is connecting to wi-fi at the same hAP the other two devices are connected to via cable.

Thank you,
Jens