When I teleport to x=30000000 and z=30000000 the world blocks are 1 grid apart. The player as well as other mobs cannot move. The blocks become cuboids and cannot be targeted. When the player is on the third-person camera, it jumps by about 250 pixels. Edit: The player can only move with fireworks-powered elytra.

This is currently all I know of this bug.

Regards to the creators of Minecraft.