Hello, I have the same exact Problem. In fact, the Engine loads the first project that is in the projects window.
IT is a hit or miss thing, meaning it doesn’t happen all the time, but it does happen very frequently and is very annoying.
I also get that hang as well, sometimes certain parts of Unreal Engine will freeze, and mouse input will become disabled, however I can still command+q to exit and press enter to save…
Has been happening to me ever since I installed Unreal Engine, I am currently on 4.13.2 , and MacOSX