Why is my map so... messed up?

See this screenshot:

You can click it to enlarge it. As you can see, there's something... very wrong with it. Some parts of the world are shifted around, caves aren't in the right spot, etc.

Here's a closer-up view (click to enlarge):

I've found out that by saving and quitting, sometimes the map is fixed (sometimes it's just messed up in a different way again, like this one:

It stays that way until the next time I save and quit, and then it happens again (in an even different way).

This has been happening since the update. It's extremely annoying; how can I fix it?

EDIT: I've noticed that sometimes when scrolling in large map view, the map will mess up in a different way or become fixed. I have not yet found a reliable way of fixing the map, though

It looks like your map file got corrupted somehow. The safest thing to do, unfortunately, is to remove the map file and start over.

Quit Terraria, then find your Terraria player files on your computer. These should be at My Documents\My Games\Terraria\Players.

If you have more than one player, open the folder that corresponds with the player that has the map problem. There will be one or more files in the player folder with names like 490810387.map. These are all map files, one for each world.

If you have more than one, you might be able to determine which one to delete using the modified date on the file. If you just played the world that has the broken map, the modified date on that map file will be the most recent.

Deleting the map file will reset the map for the player in that world, and it will start filling in again the next time you play.