I had the same line on my screen using a mini iPad 2. DJ I Ken replyed back to me and said it was a software glitch and that some people have the problem and some people don't. He said that it was supposed to be corrected with the next firmware update. (I think it was actually DJI Go app update) got a new update, now my line is gone. I just flew today.My fingers feel like popsicles.lol
By the way, have you tried flying in sports mode at full speed and then hitting the pause button, watch your mavic stand straight up on end. stops on a dime. pretty cool.