You can use the Script Unlock GB Studio event to do this. If you place a Script Unlock event in the On Init tab of a scene, it will let the dungeon render and then start the other events. Make sure it's after the Dungeon Crawler Init event.
Note: If you're starting with a Dungeon Crawler Sprite that would be visible in the view, you'll need to add a Wait event with a 1 frame count just after the Script Unlock. This will allow the actor to update and render the sprite.