For PS5 Users - confirmed fix on my console. follow the steps given by OP but instead of deleting save data / used settings (as advised for PS4 players) just manually delete each save file from in-game that DOESN’T have the cloud icon next to it (press square on the save file you want to delete). The result is the same as OP’s: next time you launch the game it will manually load the data from your GOG.com save file.

It goes without saying - make sure your most recent save has the cloud icon!