I recently saw that a well known forum member explain that you have to pay attention to the photo to the left on the calibrating screen to see what orientation the
M3Pro has to changed to. It's waiting for you to correctly match the Aircraft's orientation each time (on it's back/on it's tail etc.) before it continues. Probably the screen text also changes, but I guess all we notice is the stalled % counter. Can someone please give credit to whomever posted the solution a few days ago as I forget, or had my EyesWideShut again...