I have the AX88U and installed Merlin firmware from day one (actually waited to buy until I was sure firmware came to this model too)

On all firmware (unknown if problem exist on orginal Asus firmware) I get some issues with 5GHz network. Devices disconnects/connects every now and then if Wireless mode is on Auto. No issues at all when on Mixed mode. Maybe it gets fixed when Merlin merge with 384.5640 (it claimes to have improved wifi stability).
Does auto mode cause trouble for anyone else?
BTW it's not that very clear if HE is enabled in mixed mode or not since the option is not visible then.