Summary:

Saving the world above the void takes the player to the nearest blocks / to the area above the blocks.

This bug affects all game modes, but in survival you will die without the "Health Boost" from the "fall".

How negative height works -Y: you will be teleported to positive coordinates +Y, even if there was an area nearby, but with negative coordinates -Y.

Steps to reproduce:

1. Remove any blocks (including bedrock) under you.
2. Exit the world by clicking the "save & quit" button (your height (Y) must be above the bedrock! (on worlds without "Caves and Cliffs" +Y, and on worlds with "Caves and Cliffs" on above -64Y)).
3. Return again to the game in your world.

Observed results:

Short description:

The player is teleported from the place from which he left the world. The player's location in the world will change and there will be blocks under the player.

If there was not enough space nearby (the player will be teleported to a place where there is enough free space, you will not be teleported to the nearest block), you will be teleported to some cave or to the surface, but if there is enough space nearby, you will be teleported nearby to an area without an abyss (no hole in the void) (the height will not be changed).

Also, you will be teleported (if you were below 0) to positive coordinates in height by blocks (+ Y). This always happens, even when "Caves and Cliffs" is on.

In survival block teleportation, you will die (no additional effects) from falling.

Expected results:

Keeping the peace should preserve your position in the world and changing the position is a mistake. The player should not be teleported anywhere if he is above the bedrock.
The world must maintain its position even behind the bedrock.

In version 1.14.0.9, the player teleports only if he was below -7 (Y) height and teleports to -7 (Y) height (under the bedrock). But never teleports the player if he is above -7 (Y).

Video:

1.17

Minecraft 2021-08-30 18-45-02.mp4

Minecraft 2021-08-30 18-58-19.mp4

1.14

Minecraft 2021-09-03 09-35-48.mp4

Minecraft 2021-09-03 09-29-37.mp4