I've uploaded a new version that addresses this issue. Can you try if it fixes the problem for you?No ancestors. I was just going for a small area around the Apollo 11 landing site.
But I kind of guessed that it might be a problem, that's why I mentioned export.
For elevation the tool generate the higher level tiles as needed. At least I can export L17 elevation tiles with valid data. I guess that it generates the missing levels on export, preventing any errors on import. Perhaps the same approach for surface ?