Walkthroughs for custom maps.

And what is this flag change bug, what kind of beast is it, and under what circumstances does it occur?

Here. It works as shown in the video, with a slight randomness (it may occur if you click on a random map and then start a single-player map). It was actually banned in SoD_SP after that, so if you have the latest +/- version, you don't have to worry about it.