When a player teleports outside the world border and changes the gamemode to survival mode the player starts taking damage, but that doesn't seem to happen when next to the world border even though you're still outside.

How to reproduce

1-Start by teleporting outside the world border using the following command:

/tp 29999999 256 29999999

2-Then switch to survival mode and you will start taking damage since you're outside the world border.

3-Get a little closer to the world border and you will stop taking damage even though you're still outside.

Observations: When near the world border outside, you stop taking damage.

Expectations: You still should be able to take damage since you're still outside the world border.

Note: This may also work as intended because of the following command automatically set as 5 leading to "damage buffer" distance to be a little farther from the border.

Fix: Setting the "damage buffer" distance to 0 fixes this bug and allows any player to be damaged, use the following command:

/worldborder damage buffer 0

"Damage buffer" distance should automatically be set to 0 even if its working as intended.