Howdy. I have been using an iPhone 6 for awhile to fly my drones. With my phantom 3 standard it works fine, but with my Mavic air 2 it is constantly giving me the cpu overload error and overheating. I had an over a minit lag in the video transmission!! That can be very dangerous. I have decided I need to upgrade to an other phone. What is the oldest iPhone (newer than the 6) that I will actually be able to use? I don’t really want to spend over 100 dollars if possible.