Just to clarify... Was the iphone connected to a Skycontroller 3 via usb and the drone was connected or directly connected to the drone?
The iphone was connected to usb on controller with
phone wifi off and in airplane mode
Using controller with smart device the connection is made between the controller and drone
In this case the smart device on the most part is just a display along with providing GPS for phone and some telemetry readings
I set network connection in FF6 to manual and usually select an upper 5ghz channel - auto setting tends to drop connection if there is interference in the area
I thought I saw another post from you early yesterday with some of the troubleshooting you had performed and was thinking it sounded like a bad usb port on controller
I went back to look for post to respond but was unable to locate it, others have had issues with usb connector
Glad you were able to return for replacement a very good decision!
Once you receive it if you encounter problems just post to forum, likely someone here will be able to provide guidance
btw. for future thought there are some benefits to using an android device utilizing a modified version of FF6 that provides voltage readings while flying
Are you located in the US?
Wishing you the best of luck and happy flying