AiMesh Node For RT-AX89X

[NeedForSpeed]

I have a Asus RT-AX89X centrally located up high in the middle of the lower level of my two story 2,500 SF house. In my master bedroom using the Android SpeedTest app and WiFi 5 I'm getting ~500 Mbps. However, my Echo 8 lags whenever I try to play HiFi Tidal FLAC tracks on there (yes, I know, uncompressed music is a waste on low end equipment).

I didn't have this problem when I had a ZenWifi AX AiMesh node in the same room backhauled through MOCA. Why do you suppose that I'd still getting buffering at ~500 Mbps from the main router? Is it a setting in the router that it doesn't like? Would It help or hurt to wire up a RT-AX68U node in that room through the MOAC backhaul?

Thanks much for any ideas.