Alright, here's screenshots.
This is the screen in which the oddness happens:
There are nothing but standard "teleport player" and "show message" events, and there is one event (on the left-hand side) that requires that you have a certain item equipped before you can go that way. None of the events here seem to be the problem.
Here's the script for the event that seems to trigger the weirdness, though it seems to be alright too:
As you can see, there's no relation between this event and the screen in which the fade-out happens, yet the fade-out only happens after triggering this event. It also ONLY happens in this particular map, and ONLY if you try to walk up at any time after the event. You can exit the map from the bottom and come back around to it from the maps on either side of it, and walking up then will still trigger the fade-out. I'm really at a loss here, guys.