I was modding with Vortex too, even if you uninstall the mods with that it still doesn't really get rid of anything, so avoid using that and use a different mod manager from Thunderstore.io like r2modman. Or just do it manually if you're only using a few simple mods. I didn't really need a mod manager for the few basic ones i wanted. It's really simple to install mods manually.

Also I found when you uninstall the game, it doesn't get rid of any extra files you put into the directory. I had to manually delete everything from my Valheim folder so it was completely empty, then reinstall.

a bit messy but A) rename the current .exe for valheim.

OR Alt A )uninstall Valheim

then
B) Install fresh in a new location. .. NO MODS ..see how you go! sounds heaps like a mod manager issue or a dud (old) mod.?? GL !! if it works
C) go back to old file structure and find your world and char files and transplant them back in

I used vortex to install and uninstall.

I have verified.

Did you paste the file into your actual game files, then delete it? If you did, did it replace something and made you confirm the replacement? Either way will break your game.

Modfiles typically don't contain the entirety of the file they modify, only a section. The proper mod folder you're supposed to download and use Merges the modfiles with the gamefiles in a way that's easily removable. If you replace actual gamefiles, you'll lose like 90% of the file's contents, since you're only adding a tiny part of modified code. Never replace the actual game files, lots of people don't include all the file's contents simply because it's too much filesize.

If you did use proper modding installation, have you tried Verifying your Steam Cache? That usually fixes any problems with faulty files.