I was making a world map and I decided to add in the cactus scenery that was used in SMB: A New Beginning but unfortunately when I saved it I got this.
I started up SMBX normally checking disable frameskip and I tried multiple times to add the cactus graphic in, I can place it down but it won't save if I use it or not. Is it because it's a custom graphic or is it that I used it over a specific graphic, being the moon? And if I can't use it then...

I know for sure it has to be this graphic though because when I remove it from the folder, it works perfectly and I am able to save my map.