I'm playing a custom 1.20.1 modpack and everytime I try to open an old world it shows a screen that says, "Errors in currently selected data packs 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."
Pressing Safe Mode leads to a screen that says, "Failed to load world in Safe Mode. This world contains invalid or corrupted save data." I have tried making new worlds and it's always the same, I'm able to get into the world the first time then can't rejoin it.
Here is a log from when I tried to open the world, https://pastebin.com/9wAvHWwL
And this is the entire latest log, https://mclo.gs/qkf06Ns