There's duplicate content on my site
Are you seeing two of the same entries? (or pages, assets, etc) If so, there may have been two files with the same ID in the front matter.
This is fairly common to see when people copy/paste files and forget to remove the IDs.
The solution is usually to just remove the duplicate ID and clear your cache.
If it wasn’t a duplicate ID causing the problem, it may just have been a glitch in the matrix. Let us know what went wrong and what you were doing, and we’ll get that fixed up.