Buggy for me too. Kept telling me to choose a valid template style, but the only option was to change to an un-ordered stack, which I did and it saved. But for some reason didn't actually save the changes I made.
So I went to edit it again and it automatically numbered the games in order again but asked for me to choose a valid template? Only the option to un-order the stack was gone. Really annoying.
Edit: I know this system can work because ComicVine uses the exact same system for their lists, and it works fine.