Try with just WPA2. see this if > 1 SSID on a radio.
Avoid DFS channels, at least for testing. Using DFS channels implies at least 60s wait time before the channel may go up - and mwlwifi has never been good dealing with DFS to begin with (meaning it may fail if a radar is detected).
it's been a day and there isn't any radar on this frequency around here (plus the AP is in the basement)
FYI, I tried with openwrt-22.03.0-rc6-mvebu-cortexa9-linksys_wrt1200ac-squashfs-sysupgrade and also had issues with 5 GHz using WPA2-PSK/WPA3-SAE Mixed on WRT1200AC v2. I rolled back to openwrt-21.02.3-mvebu-cortexa9-linksys_wrt1200ac-squashfs-sysupgrade and everything seems ok now on the 5 GHz.
It'll be interesting to see how the final release of 22.03 does for people. Looks like it was just released.
I just did a sysupgrade to 22.03 from 21.02.2, keeping settings. I'll report back if I notice anything problematic.
For me the wifi 5g problem persists with 22.03
FYI, I tested my WRT1200AC v2 with 22.03.2 (Fresh) yesterday and 5 GHz issues still happening with mixed WPA2/WPA3 PSK. I am currently running 21.02.5 (Fresh Install) and all is running well as main router and AC on 5 GHz and N on 2.4 GHz both with mixed WPA2/WPA3 PSK.
Any updates for 22.03.x?