I do not have an Iphone, I am using an Ipad Mini running IOS 9.3.5 which is the latest software it can use.
I tried deleting the Mobile Terminal and reinstalling it but he problem is still there.
It seems strange that all the other functions work except the servo centre ajustment.
I can not find any detailed instructions or video on ajusting the servo centre position.
I am moving the transmitter stick to move the servo to the new centre position then pressing the start which is when the app crashes.
When the app crashes the receiver stops working until I recycle the power.