There is a bug in DJI Fly app (IOS version), where it is impossible to save Channel selection in AUTO mode, as it always reverts back to MANUAL.

Hello there NightMark. I am sorry for the trouble this has caused and thank you for giving out these information.  I will cascade these information to the designated DJI department for further attention and evaluation. For the latest DJI updates. Kindly please stay tuned or visit our DJI official website at www.dji.com. Again, thank you for your valued support and please stay safe always.