Yes, it can be replicated. I'm on a Mac with Chrome as my browser fyi. I just inputted 320x180 pixel size for my image and hit export. Half the picture is white. The other half has the space background image. Is it because it only does 200x200 tiles?
Alright thanks! It should work with other sizes than 200x200. Uploaded a new version that hopefully fixes it. If it doesn't work feel free to let me know.