You'll probably receive better answers if you ask in the DJI Mini 2 forum.
Are you sure the iPhone 7 can handle 4K video? Could the resolution be limited because of the limits of the phone?
Hello there Gord1. I am sorry for the trouble this has caused and thank you for reaching out. Can you please check if the said mobile device ( iPhone 7 Plus ) that you are using can process and upload a 4K video? In addition kindly please try using a different recommended mobile device for the DJI Mini 2 for us to be able to isolate the said issue? Thank you.