World Chunks disappearing when reopening world after update 1.20.1

Regression Builds = 1.19
Partner Team Reporting = Noxcrew
Impact = This may have a major effect on reviews; players are unable to play the map correctly. Users losing progress in existing worlds
Summary = World Chunks disappearing when reopening world after update 1.20.1
 
Partner Rank: 1
Verification builds: 1.20.1
Impact: Affected Players are no longer able to engage with our content, which could have a major effect on reviews
Repro Steps: Download the mcworld attached and import it into Minecraft
Go to the Marketplace and Download City Living 2 (This will make sure the world has the missing Resourcepack and Behaviourpack)
Load the world you imported world (Make sure the Resourcepack and Behaviourpack are not missing)
Observed Results: The world chunks are gone, apart from some that are left. Able to engage with Entities
Expected Results: World chunks to be present and loaded correctly
Screenshots/Videos attached: Yes
Regression Build: