I have a world created with a custom 1.18.1 Modpack, and now I am trying to upgrade it into 1.18.2.
I replaced all mods from the original pack into their 1.18.2 versions. The new pack is launched successfully, but when I try to load the old world, it says "Errors in currently selected datapacks prevented world from loading".
Based on my own experiences, upgrading the mods and load an old world may have problems if it contains some blocks/items/entities which is already removed in the newer versions.
However, I am sure that the world does not contain any of removed blocks/items/entities. Also,
When I tried to load a world created with the old 1.18.1 pack containing only vanilla elements, it shows the exactly same error message.
When I tried to load a world created with vanilla minecraft, but have been loaded, modified and saved with the old 1.18.1 pack, it opens successfully.
It makes me even more confused what the problem is.
Both the old 1.18.1 pack and the 1.18.2 pack only have built-in resources packs loaded. (Default Minecraft, mod resources and a built-in resource pack for the mod supplementaries)
The debug log file is pasted here:
https://pastebin.com/LB9niyib
I have also checked the log myself before, but have got not idea what happened. The errors don't seem to point to a specific mod or a data pack.