I've been getting some pretty severe lag when first entering a singleplayer world or a multiplayer server. The lag is also pretty bad when travelling to an area with chunks that were unloaded, so the lag seems directly proportional to how many chunks the game is attempting to load at once. This issue wasn't present in any previous version, including the initial 1.16 release, so it seems the 1.16.1 update is what caused it. I've tried everything to see if it was an issue on my end, and nothing seems to change the effect at all. Downgrading to previous versions fixes the issue.

How to replicate: simply enter a world. The game will take a significant amount of time to even reach 1 frame per second.