When rejoining singleplayer world for the first time and after, massive lag spikes when crossing chunk border.

So I started a world in 21w16a with the Caves & Cliffs preview datapack on. After leaving the world for the first time and restarting it right after, massive lag spikes would occur when I cross a chunk border.

Here's a link to a video I made showcasing this bug:

https://youtu.be/W8E8_l_PpYM

 

 

I just wanted to make a survival world and play a bit checking the new things out along the way and stuff, but this just makes it unplayable...