I'm of the opinion its our fade mechanic. Due to the UI sitting in front of this black screen, the only thing I can think of that would do that is the fader. The fact that you can hear the sounds tells me the game should be playing. We're exploring options for a test of this.
The save system is pretty simple, if it can't find any data, it just creates a new data type for it. I didn't create it and we might end up refactoring the whole thing. Its not a bad system, its just complex enough to be annoying to work with imo.