Variety of asserts on world load for some worlds

Verification builds: Release 2555018 - 1.12.0.28 RC3
Summary: Loading up the world for Relics of the Skies (and at least one other in development project) causes a variety of asserts to fail.

Repro Steps:
1. Run a Release version of Minecraft with 'Assertions show a modal dialog' enabled, and disable 'Assertions break in the debugger' to allow multiple assertions to show.
2. Download and create a world for Relics of the Skies from the marketplace.

Observed Results: Most of the time, a large number of asserts will pop up one after another. Occasionally no asserts will show, and the world will require some reloads in order for them to show. The particular asserts that show up are seemingly random, and may have relevence to where the player is located or looking.

Some examples of the asserts found:

Assertion failed: Something went wrong, the chunk wasn't loaded
Condition is false: resource.hasBlock(mMin)
Function: LevelChunk::setupRedstoneCircuit in f:\darwinwork\3\s\handheld\src\common\world\level\chunk\levelchunk.cpp @ 2279

Assertion failed: Block (minecraft:air) doesn't have the block state (upper_block_bit)
Condition is false: false
Function: BlockLegacy::getState in f:\darwinwork\3\s\handheld\src\common\world\level\block\blocklegacy.h @ 203

Assertion failed: Block (minecraft:air) doesn't have the block state (facing_direction)
Condition is false: false
Function: BlockLegacy::getState in f:\darwinwork\3\s\handheld\src\common\world\level\block\blocklegacy.h @ 203

Assertion failed: Block (minecraft:air) doesn't have the block state (facing_direction)
Condition is false: false
Function: BlockLegacy::setState in f:\darwinwork\3\s\handheld\src\common\world\level\block\blocklegacy.h @ 215

 

Expected Results: No assertions.

Impact: Some newer content is plagued by asserts of this nature, and have delayed their release time. Older projects with asserts are often met with delays when attempting to update them. There is no known impact to the player or world if play is continued with asserts turned off.

 

Additional Info: The assertions disappear when all air in the world is changed to another material, such as purpur, but return when the air is changed back. Our in-development project that exhibits the issue does not seem to have any asserts when first converted, but gains them at some point later as bedrock content is added in. The asserts seem to occur more frequently in some locations than others, and differently based on where the player faces.

I had expected to find a regression build in which the issue does not appear for Relics of the Skies, but was unable to find one - the earliest tested was 1.9.0.13_rc3. The asserts still occur in the 1.13 versions as well.