Four years later and this is still happening...
I'll be doing some world hopping, moving items around or whatever, and then randomly one of the maps (sometimes several) gets reset back to solid black on that current character. Sometimes it's not even one of the worlds that I was popping in and out on, and on the rare occasion will hit a character that I haven't even recently played.
- In other words; a specific map can reset for all characters, but not all maps will reset for a specific character.
It doesn't happen as often as it seems to with most people (i.e. resetting every time the game launches), but still it happens enough to be extremely annoying and frustrating. Also, I have never played multiplayer, so that isn't any part of the issue.
Honestly, it's getting to the point where I don't even want to play anymore.
EDIT: Was hoping the 1.4.4 update would finally fix the problem, but alas, it is still happening...