Microsolderer Jessa Jones can fix practically anything. But these days, she spends most of her time fixing just one thing. Because every single month, more and more iPhone 6 and (especially) 6 Plus devices show up at her shop with the same problem: a gray, flickering bar at the top of the display and an unresponsive touchscreen. And she's not the only one. Repair pros all over the country are noticing the same trend. Here's what we think is killing all those iPhones.