Program.Main: ERROR: An item with the same key has already been added

I was having the same problem as well. I tried looking into the *.target extension but I wasn’t sure what to delete.

Instead, I made a new blank project and migrate the root folder into the new project, loaded the input settings, change the game mode to MyGameMode and was able to have to fix the problem this way. This could possibly be an alternative if you do not want to delete any .target files from your system like me.