I've just finished going through episode 280 where Casey finishes up streaming entities and packing and unpacking into blocks.
At the start of episode 281 Casey is moving around multiple rooms and you can see after the initial few they are missing entities and look broke. Casey mentions about dodgy world gen code - however I think there is an issue with packing or unpacking entities.
If you move far enough away from the starting room which looks fine (until it leaves the sim region bounds) and then come back - you experience the same issue with missing entities and general oddness.
I've briefly look at future episodes but it seems Casey is mainly playing the game in one room whilst adding features so I am not sure if he fixes this issue or is even aware of it yet?