After much fiddling, much tweaking, and a whole lot of commenting, the bbb, black bar bug, is still not fixed, and even worse, the solution I thought I had turned out to be faulty. Prof. Medero recommended I use a static analyzer tool, prebuilt into XCode to try to find memory leaks, but this tool gave me no errors with my code, which was as I expected. In my own tests, I created a new project and stripped it down to just a VC transition and a scrollview on one of the VCs, and this still produced the bbb. I then spent a ton of time trying to convert the infrastructure of the scrolling label from a double subview of a uilabel and scrollview to a single instantiation of a text view. However UITextView is truly awful to work with. All of its functions are hallmarks of obj C, and all the functions which I needed to use have been deprecated in the current XCode implementation. The problem is that I can’t resize the text view, ever, because it resizes its vertical, not its horizontal, even if you explicitly limit its number of lines. Moreover, when you do limit lines and then ask for a horizontal increase, it does it, but also adds characters above itself in its frame. Basically, it doesn’t like being used for horizontal purpose, which is what we need. So that is out of the question. I tried using a UITextField, but this behaved in the exact same way as the UILabel. At the end of the day I tried just instantiating a bare bones scrollview with constituent label in the MVC, without any calls to creating the scrolling label, and this worked, without ever bringing up the bbb. This gives me hope, because it means there is something which is wrong in the scrolling label, I just need to find it.