Need help! "Errors in currently selected datapacks prevented the world from loading."

[Luvs]

I'm getting an error when loading up my modded world: "Errors in currently selected datapacks prevented the world from loading. You can either try to load it with only the vanilla data pack ("safe mode"), or go back to the title screen and fix it manually."

This error occurs after I open the save, return to title screen, and try opening the save again. In which, it will throw this error at me.

It appears to only happen with this save - I can load and reload other worlds without issue, which makes me think that something I recently done in my world somehow corrupted it? The last thing I did was work on my house so I placed a lot of modded blocks. I don't know if that could be the cause.

Every time I open up a copy of my save, I can open the world. But then I try re-opening it and the error occurs. So something is going on in between me exiting the world and trying to reopen it.

I tried deleted the level.dat file and replacing it with level.dat_old (renaming it to level.dat) as I saw in another thread, but that doesn't work. I am playing on a custom modpack that I made (no datapacks) and this error has occurred 30 days into my play-through of the world. It has not happened before.

Here is the console log from MultiMC after I launch my game, open a new copy of the save, quit to title screen, and attempt to open the save again. https://paste.ee/p/9CvEU

[TileEntity]

There is an issue with an entry in your level.dat

 

java.lang.RuntimeException: Tried to read NBT tag with too high complexity, depth > 512

Maybe check this file with an NBT editor

[Luvs]

16 minutes ago, TileEntity said:

There is an issue with an entry in your level.dat

 

java.lang.RuntimeException: Tried to read NBT tag with too high complexity, depth > 512

Maybe check this file with an NBT editor

Okay, what should I be looking for? Anything in particular?

[TileEntity]

I have no idea - maybe some world generation settings

 

Or check the level.dat for the seed

Copy the seed, create a new world with the same settings and the seed

Then copy level.dat, level.dat_old and session lock from the new world to the broken one

Delete the new world and test the old world again