The world border texture jumps eight pixels when moving.
It only happens if the world border is larger than 65 blocks, or you are on the outside.
It only happens on the south side of the border, and may stop after moving a few block north (larger area of effect the larger the border)

This bug is hard to notice without using a resource pack, since the default resource pack has the same eight pixels repeated

The screenshot shows that the border has become misaligned, but does not show the bug fully.

Steps to reproduce:

1. Apply a custom worldborder texture for visibility, or use the provided debug pack
2. Set the worldborder to center at your location using /worldborder center ~ ~
3. Set the worldborder size using /worldborder set 150 0
4. Travel to the southwest corner
5. Face west and travel to the north