Ok, so I just did a quick tutorial on how to edit maps, I figured it was because of some tiles on Buildings layer, idx 16, so I select all tiles, and press delete to delete every invincible buildings like that. If there were non-invincible buildings that are supposed to be there, I might have deleted those too, but I think the whole area was empty. Hope this info helps.
Yes I finished earlier, it turns out it was the invisible tiles from the previous edge of the smaller map. Sorry about that
