I was finishing a map yesterday. I decided to change it to kingmaker since the invasions don't work correctly. It wasn't long before I realised removing walls wouldn't work. I messaged in hope that he'd know a way to remove them, since he's made great maps in the past. He too noticed removing walls just wasn't accomplishable. A quick google search led me to believe this was a map editor bug. If anyone is also having this problem, please reply so I know it isn't just a coincidence. Thank you!