I'm not sure why it would only be invisible during the cutscene -- it's added separately so by the time the event plays it should just be kind of a background object, same as when the event is over. When I test your map alone (after grabbing a png to use for the missing tilesheet) or in Expanded Access, it's invisible for me either way, so that's weird.
I opened the map and resaved the zladder tilesheet + map and it works fine for me now, during or after event... not sure why it wasn't before.
I did notice when I was checking your other maps (in case the pack you had them in was relevant -- I was just guessing on where it was from) that not all of your town maps are prefixed, though. Dusty's doghouse patch isn't, and has various tilesheets saved twice for some reason. (Though CP should handle the prefixing if it's an edit patch, at least.)