[MC-190533] Very rarely, when upgrading a world from 1.15.2 to 1.16 and then throwing an item under the "piglin_loved" item tag near a Piglin, that mob would not pick up the item even after the game is restarted

The bug

In a very rare case when a world is upgraded from 1.15.2 to 1.16 and then entered, any thrown item under the #piglin_loved item tag would not be picked up by a Piglin whatsoever even after the game is restarted. This causes problems especially if the world has not been backed up beforehand, and if the bug is successfully reproduced, no errors are sent to the log either.

If the world has been backed up before being upgraded, delete the upgraded world, copy the backup into the saves folder, and then upgrade it the same way to fix the bug.

Note before reproduction

The bug has only been reproduced once. Creating a brand new world in 1.15.2 and then upgrading it to 1.16 does not easily reproduce the bug whether the method used is either optimizing the world without erasing cached data, doing the same with erasing cached data, or loading the world directly without optimizing it. It has been reproduced by upgrading an old world from 1.15.2 to 1.16 using the "Optimize World" feature without removing cached data.

In case anyone is interested in reproducing the bug, an old world from 1.15.2 can be found soon for it to be upgraded to 1.16 with any method.

If anyone has been able to find a consistent manner of reproducing the bug, please share it in the Comments section below.

Log

Here is the log output when attempting to recreate the bug:

> [19:33:48] [Render thread/WARN]: Ambiguity between arguments [teleport, destination] and [teleport, targets] with inputs: [Player, 0123, @e, dd12be42-52a9-4a91-a8a1-11c01849e498]
> [19:33:48] [Render thread/WARN]: Ambiguity between arguments [teleport, location] and [teleport, destination] with inputs: [0.1 -0.5 .9, 0 0 0]
> [19:33:48] [Render thread/WARN]: Ambiguity between arguments [teleport, location] and [teleport, targets] with inputs: [0.1 -0.5 .9, 0 0 0]
> [19:33:48] [Render thread/WARN]: Ambiguity between arguments [teleport, targets] and [teleport, destination] with inputs: [Player, 0123, dd12be42-52a9-4a91-a8a1-11c01849e498]
> [19:33:48] [Render thread/WARN]: Ambiguity between arguments [teleport, targets, location] and [teleport, targets, destination] with inputs: [0.1 -0.5 .9, 0 0 0]
> [19:33:48] [Render thread/INFO]: Reloading ResourceManager: Default
> [19:33:48] [Render thread/INFO]: Loaded 7 recipes
> [19:33:48] [Render thread/INFO]: Loaded 927 advancements
> [19:33:49] [Render thread/INFO]: Environment: authHost='https://authserver.mojang.com', accountsHost='https://api.mojang.com', sessionHost='https://sessionserver.mojang.com', name='PROD'
> [19:33:51] [Server thread/INFO]: Starting integrated minecraft server version 1.16 Release Candidate 1
> [19:33:51] [Server thread/INFO]: Generating keypair
> [19:33:51] [Server thread/INFO]: Preparing start region for dimension minecraft:overworld
> [19:33:53] [Render thread/INFO]: Preparing spawn area: 0%
> [19:33:53] [Render thread/INFO]: Preparing spawn area: 0%
> [19:33:53] [Render thread/INFO]: Preparing spawn area: 0%
> [19:33:53] [Render thread/INFO]: Preparing spawn area: 0%
> [19:33:53] [Render thread/INFO]: Preparing spawn area: 0%
> [19:33:54] [Render thread/INFO]: Preparing spawn area: 44%
> [19:33:54] [Render thread/INFO]: Preparing spawn area: 89%
> [19:33:54] [Render thread/INFO]: Time elapsed: 3311 ms
> [19:33:56] [Server thread/INFO]: Changing view distance to 12, from 10
> [19:34:03] [Server thread/WARN]: Ignored advancement 'minecraft:husbandry/break_diamond_hoe' in progress file C:\Users\HP\AppData\Roaming\.minecraft\saves\Old World in 1.15.2\advancements\00000000-0000-0000-0000-000000000000.json - it doesn't exist anymore?
> [19:34:04] [Server thread/INFO]: Boyrex[local:E:f52fa05b] logged in with entity id 92 at (70.15575590208633, 56.0, 936.8851313296918)
> [19:34:04] [Server thread/INFO]: Owner Boyrex joined the game
> [19:34:04] [Server thread/INFO]: Saving and pausing game...
> [19:34:04] [Server thread/INFO]: Saving chunks for level 'ServerLevel[Boyrex's Contraptions]'/minecraft:overworld
> [19:34:05] [Render thread/INFO]: Loaded 675 advancements
> [19:34:06] [Server thread/INFO]: Saving chunks for level 'ServerLevel[Boyrex's Contraptions]'/minecraft:the_nether
> [19:34:06] [Server thread/INFO]: Saving chunks for level 'ServerLevel[Boyrex's Contraptions]'/minecraft:the_end
> [19:34:08] [Server thread/WARN]: Can't keep up! Is the server overloaded? Running 5350ms or 107 ticks behind
> [19:34:18] [Render thread/INFO]: [CHAT] [Debug]: Reloading all chunks
> [19:34:27] [Server thread/INFO]: Saving and pausing game...
> [19:34:27] [Server thread/INFO]: Saving chunks for level 'ServerLevel[Boyrex's Contraptions]'/minecraft:overworld
> [19:34:27] [Server thread/INFO]: Saving chunks for level 'ServerLevel[Boyrex's Contraptions]'/minecraft:the_nether
> [19:34:27] [Server thread/INFO]: Saving chunks for level 'ServerLevel[Boyrex's Contraptions]'/minecraft:the_end
> [19:34:38] [Server thread/WARN]: Can't keep up! Is the server overloaded? Running 2027ms or 40 ticks behind
> [19:34:38] [Render thread/INFO]: Loaded 675 advancements
> [19:34:42] [Render thread/WARN]: Received passengers for unknown entity
> [19:34:42] [Render thread/WARN]: Received passengers for unknown entity
> [19:34:42] [Render thread/WARN]: Received passengers for unknown entity
> [19:34:42] [Render thread/WARN]: Received passengers for unknown entity
> [19:34:56] [Render thread/INFO]: [CHAT] Set own game mode to Spectator Mode
> [19:34:56] [Server thread/WARN]: Can't keep up! Is the server overloaded? Running 2961ms or 59 ticks behind
> [19:35:03] [Render thread/INFO]: [CHAT] Set own game mode to Creative Mode
> [19:35:06] [Render thread/WARN]: Received passengers for unknown entity
> [19:35:06] [Render thread/WARN]: Received passengers for unknown entity
> [19:35:13] [Render thread/INFO]: Loaded 676 advancements
> [19:35:15] [Server thread/WARN]: Can't keep up! Is the server overloaded? Running 3986ms or 79 ticks behind
> [19:35:34] [Server thread/INFO]: Saving and pausing game...
> [19:35:34] [Server thread/INFO]: Saving chunks for level 'ServerLevel[Boyrex's Contraptions]'/minecraft:overworld
> [19:35:35] [Server thread/INFO]: Saving chunks for level 'ServerLevel[Boyrex's Contraptions]'/minecraft:the_nether
> [19:35:37] [Server thread/INFO]: Saving chunks for level 'ServerLevel[Boyrex's Contraptions]'/minecraft:the_end
> [19:35:37] [Server thread/WARN]: Can't keep up! Is the server overloaded? Running 2423ms or 48 ticks behind