iKorbon

This problem affects 1.17.40 as well.

I can confirm this still happens in 1.17.30-1.17.32. I also noticed this happens across different devices, but most commonly happens if you apply a custom biome addon on a Realm. The climates, fog color, water color, etc. are all mixed and don't match their correct biomes. You can still reproduce this by doing what is said in the original post, or you could apply the biome addon to a Realm and you will encounter the problem pretty quickly from my experience.

To reproduce steps:

1. Create a custom block using the ticking component.

2. Save the custom ticking block in a structure.

3. Make the structure generate in the world using features, and make the scatter chance high to have it spawn frequently.

4. Start a new world.

The results of this should either be the game completely crashing, or the world going into a "frozen" state where no new chunks will load, no mobs will move, etc.

I have attached an addon showcasing the problem above with a large structure. Experimental toggles must be enabled. 

To reproduce this bug, just make a structure larger than 48x48, save it as a structure and make it spawn naturally in the world using features ad feature rules. Give it a high scatter chance so you don't need to look long. It doesn't happen all the time, but happens pretty frequently. It seems to cut off structures at chunk borders, Even small structures have a chance of getting cut at chunk borders, but large structures are almost always cut.