Nighthawk AC2200 WiFi Extender (EX7700) disrupts iphone 5G connection

[k01gj01k01gj01]

I setup my Nighthawk AC2200 WiFi Mesh Extender following the usual steps. I can connect my laptop to both the 2G and 5G extended networks. But I can only connect my iphone to the 2G network. When I try to connect the iphone to the 5G network I am prompted with incorrect password. I know the password is correct. If I turn off the extender I can connect to the 5G network with my iphone. 

Unsuccessful troubleshooting steps so far:

Power down each device (router, modem, extender, iphone) one by one and check for complete connectivity. 

Forget the 5G network in the iphone settings.

Reset the iphone network settings to default.

What is going on here?

I'm using a Spectrum leased router and modem.

[DavidRC]

Which firmware do you have? The recent firmware update (.210) resulted in authentication problems for me on the 5GHz band with my Android mobile and tablet. Going back to the .206 firmware solved the authentication problems. See:

https://community.netgear.com/t5/WiFi-Range-Extenders-Nighthawk/EX7700-Firmware-210/m-p/1972650/high...

https://community.netgear.com/t5/WiFi-Range-Extenders-Nighthawk/AC2200-EX7700-Mesh-Extender-Dropping...

https://community.netgear.com/t5/WiFi-Range-Extenders-Nighthawk/Appalling-Support/m-p/1974423/highli...