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

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/highlight/true#M42402

https://community.netgear.com/t5/WiFi-Range-Extenders-Nighthawk/AC2200-EX7700-Mesh-Extender-Dropping-Connection-after-210/m-p/1973433/highlight/true#M42454

https://community.netgear.com/t5/WiFi-Range-Extenders-Nighthawk/Appalling-Support/m-p/1974423/highlight/true#M42530