It’s no secret that Nintendo will happily delete uploaded Super Mario Maker 2 courses that break the guidelines concerning course content, glitching, or various other reasons that no one can figure out, but apparently Nintendo can now also delete your levels even if you haven’t hit that upload button.
A report out of Kotaku says that after they created a level with a “black hole glitch” (the glitch that allows users to layer items on top of each other, endlessly cloning the items) was deleted, despite never actually uploading it. The removal happened after saving and returning to the Coursebot menu. They were shown a screen with a text box saying “corrupt data was found so the course has been deleted.”
This suggests Super Mario Maker 2 has been designed to detect course glitches and clear out this content immediately. It doesn’t matter how much time or effort you gave to the rest of the course, if there’s a glitch, it’s gone—even if you had no idea there was a glitch in your material in the first place.
Sometimes, the user has apparently been allowed back in to fix the parts causing the error, but this only happens if the error message appears during the saving process. If the game detects the glitch after a course has been saved, there’s no recourse (pun absolutely intended)—your level will disappear.
If you’re knowingly trying to create glitches in the game, you’ve probably expected something like this to happen, but for those who are simply trying to create fun content, this is worth being aware of as you play around with the material and inevitably discover glitches along the way.