Crossing the world border on Earth (with the intention that it wraps around) completely soft-locks the game, resulting in graphical glitches that make it appear like I'm underwater and freezing the logic thread. I also cannot open the map or photo mode in this situation, and trying to access the addon editor in this soft-locked state crashes the game.

This was tested on two separate occasions at 10km and 19km altitude flying at 1900 km/h and 600 km/h respectively.

I do not have the space DLC. Even if this is intended behavior (no wrap around unless you have the DLC), crossing the border should still not result in the game becoming unplayable.