renpy keeps a copy of saves in a hidden folder, that's how you find your saves from older versions whenever you download an update.
to see and delete them, first go to your user folder (it's whatever you named your pc, like, it has my name and surname here), make sure you can see hidden folders! while in a folder, click on "view", that should show an option to let you see hidden files/folder/items. Now, in your folder you should see "AppData", click on it, then "Roaming", "RenPy", "Tvern_of_Spear-1" and delete the faulty save file from there AND the "sync" folder.
If you don't know which save is which, the name is based on the page and position the save shows up in the game, like, a save at page 8 in the bottom right will be named "8-6-LT1,save", so i hope you remember its position (since you can't check due to the error).
(don't touch the persistent save btw, that has precious stuff like gallery and such)
Here's a pic to see what is where (remember that AppData itself is found inside the users folder, which has your pc's name)
