You shouldn't get stuck. Just walk back across those tiles. It never kills all your mons, there will always be one left alive. I'm not sure if it already applies at that point, but you can control the panels with the 'a' button.
The game is not broken at that point
You can also do a ground mono. It might be a bit difficult at the beginning, as there aren't that many ground types yet, but once you gain access to the cave under the grand stairway, you have a lot to choose from