Teleporting tick_world entities into unloaded chunks may wipe block entity data in nearby chunks

Partner Rank:

1

Partner Team Reporting:

Everbloom Studios

Verification builds:

1.16.0.61

Summary:

Teleporting tick_world entities into unloaded chunks may wipe block entity data in nearby chunks.

Impact:

Makes the use of tick_world entities potentially hazardous to the map's functionality, as it may wipe the command blocks in those chunks. May also wipe some of the player's stuff from chests nearby. 

This again may affect one of our maps that has been blocked by bugs for nearly a year.

Repro Steps:

1. Join the provided world. There should be a glowstone-block-like entity above a command block. This entity has a tick_world component.
   The chat should be spamming "Found" when the Tick entity is loaded, and "Not Found" when it's not loaded.
2. Press the button to teleport the Tick entity "Away" and "Here", going back and forth between them (the chat may say "Not Found" for a few seconds when teleporting away, might have to wait for the game to get around to loading those chunks before teleporting it back).
3. Every now and again press the button on the command block labeled "Tp You Away" to go to the chunk the entity is being teleported to and observe the three command blocks in that area

Observed Results:

Sometimes you'll see that some, if not all of the three command blocks in that area have been wiped. They normally have labels on them, and should mirror the three command blocks in the other area, teleporting the tick entity back and forth and teleporting you to the other area.

Not sure if this is causation or just correlation, but most of the time when the data is wiped, the chunk takes a little longer than usual to load. Most of the time it can load within less than a second; but when the data is wiped it takes 2 or more seconds. This could just be coincidence though.

Expected Results:

The data in the command blocks should not get wiped, no matter how many times the entity is teleported.

Screenshots/Videos attached: Yes/No

Yes

Regression Builds:

1.14.60 (latest build of 1.14). Cannot efficiently test in later versions up to 1.16.0.60 due to MCM-995

Notes:

Video