I got the OTG adapter and USB to Lightning cable for connecting my iPad Mini to my Sparks RC.  It seems like all the settings are the same as before, except my C and Fn buttons are no longer assigned any function.  I can assign functions to those buttons, but when I disconnect the phone from the RC, and reconnect everything, the button settings are lost again.  I can then connect the phone to the RC over wifi again and the settings are retained.  Anyone else losing the C and Fn button settings when connecting to the RC using OTG and USB cable?

Same here.  They have to be reassigned every flight.  I plug in the phone to the controller so that must be the issue.

You also lose ability to change the flight mode back to Mode 2 if you've changed away from it. Seems likea few of the DJI GO4 settings are not being saved when using the cable.