Since I played defense, I can’t get any other map than the defense map to be used when starting a new game, help!
I assume you deleted the save folder already?
The problem would almost certainly be with the save folder.
Move it out of the game folder. Try the game.
Does it work properly now?
You have found a horrible bug for the devs. Send as much details to them, including both save files and most likely the entire game.
Delete the NEW save and move the old one back in. See if it fails again.
If it fails again:
It is a problem with the save. Give it to the devs for bug solving. Then delete it and continue playing C:DDA.
If it works, finish imploding the universe. For !SCIENCE!