I'm using 18.4.1, which could be the issue.
The game doesn't crash or throw any errors, it's just a visual thing. Inside, maps repeat at the borders, and outside, other maps sometimes overlap over the correct area, making the player character invisible and making navigation rely entirely on memory. I'm downloading 18.4.3 now, with any luck that fixes it. Thank you!
EDIT: Yep! That fixed it. Surprised it did that rather than crash the game entirely.