Luvs

Great news! That actually fixed it! I am forever grateful for your help man, you seriously saved me. Here is exactly what I did in case others have the same issue: Create new world (using the re-create world function didn't work for me.) Use the same seed from original world, make sure my game settings are all the same like difficulty, gamemode, etc. Load in to world. Exit world. Go to save folder, copy level.dat, level.dat_old, and session.lock Go to original broken world's save folder, delete those three files and paste in the ones I copied. Load into original world. I relogged a few times just to check the error wouldn't return. Seems now to be working just fine! I'll be making sure to make more frequent backups and if this problem ever occurs again, I'll try out your solution once more. Thank you again TileEntity!

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

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