I've started to notice problems with 5ghz on my AX1500.  The 5G SSID is visible, but when I try to connect to it, it won't connect.  It just keeps repeatedly trying to connect.  If I restart 5G wireless or reboot the router, it starts to work again.  Is there some setting or trick to get it to work properly?  2.4 ghz seems to be fine so far.

The 5G setting is pretty basic:

Smart Connect is disabled.

OFDMA is enabled, but greyed out.

TWT is disabled, but greyed out.

WMM is enabled.

AP Isolation is disabled.

Airtime Fairness is disabled.

Security:  WPA/WPA2 Personal

Version:  WPA2-PSK

Encryption:  AES

Transmit Power:  High

Channel Width:  80MHz

Channel:  36

Mode:  802.11a/n/ac mixed (I have ax disabled since I have no ax clients and I've heard there are problems with it)

My regular wireless clients are android phones, which operate in N mode, and a media player that is 5G AC, but only used occasionally.