Please help!

Router was running 2.1.2 Build 20210901 rel.75681(4555) with no problems whatsoever. Received notification to upgrade to latest revision, performed the upgrade via Router UI and upgraded to 2.1.5 Build 20211231 rel.73353 which completed with no errors and router rebooted.

Waited for router to fully start, 2.4GHz Wifi works with no issues as does LAN connection however 5GHz Wifi not working (SSID not visible on laptop, unable to connect) despite router telling me it is on.  Turn off 5GHz Wifi and turn back on again, 5GHz wifi still not working and 2.4 GHz Wifi also stops working (SSID's not visible on laptop, unable to connect to either).  LAN connection still okay.  Turn off 2.4GHz Wifi and 5GHz Wifi then turn both back on again, no change, both 2.4GHz Wifi and 5GHz Wifi also not working (SSID's not visible on laptop, unable to connect to either).  LAN connection still okay

Turn off power to AX20, wait 10 seconds, turn back on again and wait for router to fully start

2.4GHz Wifi works with no issues as does LAN connection however 5GHz Wifi not working (SSID not visible on laptop, unable to connect) despite router telling me it is on.

On system Tab > Backup and Restore: Select the "RESTORE" button that will 'Restore all configuration settings to default values, except your login and cloud account information'.  Wait for AX20 to reboot and fully start, no change 2.4GHz Wifi works with no issues as does LAN connection however 5GHz Wifi not working despite router telling me it is on.

Revert firmware back to 2.1.2 Build 20210901 rel.75681(4555) via download from TP-link website and setup Wifi SSIDs and passwords to what they were before the upgrade,  everything now works correctly, 2.4GHz Wifi, 5GHz Wifi (same laptop can now see 5GHz SSID and connect with no problem), LAN connection :-)

I notice that on the TP-link UK Website foir AX20 V2: https://www.tp-link.com/uk/support/download/archer-ax20/v2/#Firmware

The latest firmware listed is Archer AX20(EU)_V2_210901 which is 2.1.2 Build 20210901 rel.75681(4555) not the 2.1.5 Build 20211231 rel.73353 that the router upgraded itself to.

What is happening here?  Am I doing something wrong or is there a problem with 2.1.5 Build 20211231 rel.73353 ?

I notice that the new 2.1.5 version mentions "1.Improved wired and wireless stability" in the list of enhancements, could this be the cause?  Due to the way I use the AX20 the passwords for the 5GHz Wifi are quite long (32 characters) could this be part of the problem?

Help please!

Thank-you.