I had the same issue. I had to revert back to 4.12.5 because Apple doesnt allow massively long black screens like that. My loading screens are twice as long as yours on iphone 6s plus. Before, it would only take about 1-3 seconds to open a level and my loading screen would bridge the gap. Now it is taking about 10 seconds … even when it loads a basic UI only map (Start game screen).