Sometimes when you place a redstone dust one block behind a world border, some chunks around that redstone dust don't render anymore. Somehow after a while it fixes itself, but the redstone dust doesn't have a texture anymore(basically invisible). You can only find it with the hitbox of the dust.

How to replicate:
1. Set world border to something small´
2. Go to the world border
3. Place a redstone dust behind the border
4. Try Step 3 a couple of times until the world doesn't render anymore.