One other thing has just come to mind, your comment about stopping the props.
There is a stick position known as CSC, it is both control sticks fully back AND simultaneously either fully towards each other (down and in) or fully away from each other (down and out), with the combination being held for a certain period of time. You might use the combination to start the motors.
With the motors running it is supposed to stop them.
In the fly app the function has two modes of operation. For me, with the mini, they are called "anytime " and "emergency only".
In "anytime" mode the position seems to stop the motors after it has been held for around 2 seconds and that is irrespective of whether the drone is in the air or on the ground, I did some low altitude testing of this and the mini fell about 18" onto grass.
However and I have bug up my .".....".about this, in "emergency only" mode it will apparently only stop the motors when the drone decides that it has encountered an emergency e.g. it HAS crashed into something or IS tumbling etc.. To my mind the drone is already going to be coming down in an uncontrolled descent after such an emergency so why would it be of use to stop the motors?
It would probably have worked in the situation where you wanted to stop the motors and it may indeed have been what you did use and in the light of your exprience I can now see some point to that mode. I would however like to stress that it seems it will NOT stop the motors if the drone is in normal flight .i.e if the function was in "emergency only" mode and your drone was being blown away and towards a town or crowd you could not drop the drone, or if an aircraft suddenly appeared and was on a collision course with your drone you could not drop it. In such circumstances In order to drop the drone It would be necessary to switch to "anytime " mode and then execute the CSC.
Infact in one of my recent flights to test this I sent the mini up to 100+m then held the CSC position all the way down to around 2m, it was a 'controlled' descent the whole way down and as soon as the sticks were released it hovered.