AirPlay/WMM Issues RAX75

AirPlay keeps cutting in and out when using 2 DEVICES. It eventually drops out completely. I tried AirPlay with an older iMac on ethernet, and a 2018 MacBook Pro on 5GHz, to TWO clients (Apple TV 4K and Apple TV 3rd Gen). The third gen (older) Apple TV on 5GHz WiFi is more reliable. Both clients have EXCELLENT connection and I can stream Plex so I know it's not the signal. Apple TV 4K is ethernet as well. Both devices are up-to-date.

Side note: I tried to disable WMM to see if that would help, but when I do I get an incorrect password on WiFi all WiFi clients. Will not accept the password if entered again. QoS is diabled. I'm speculate that there's a serious bug with WMM.

RAX 75 Firmware: V1.0.3.98_1.0.46