Why does my structure sometimes not place?

Long story short: I am making a skyblock around eating stuff. The Nether is reached by eating obsidian, which is supposed to generate an Island and tp you to those coords. The tp part works fine, and I thought the Island was too. But the structure seems to only place half the time. I don't know why it is so inconsistent? I think it might be something about the nether not being generated when the command is run, but IDK how to fix that...