Troubleshooting & messages · Free space and clean-up messages
Why does it say a drop in space couldn't be tied to one app?
Short answer: The change was spread out or happened in areas Storage Studio can't read, so it won't guess a culprit. Watch What's Using Space over a few days if space keeps vanishing.
Storage Studio looks for the folder or app behind a change in free space. Sometimes the change is spread across many places, or happened in system areas it isn't allowed to read — so it says it couldn't pin it down rather than name the wrong culprit.
It's not an error. If space keeps disappearing, check What's Using Space over a few days to see which folders grow.