Duplicate Internal Identifiers?

I would like to know what this is referring to and what might have happened to cause it. Thanks.

This is explained in §23.2.7 of the user manual (you can find it searching for “duplicate ids”); there’s a bit more, so worth checking, but as far as the possible cause: “Duplicating [Compile] Formats from within Scrivener is safe and often useful to do. Problems can arise if the files used to store formats on your disk are duplicated outside of Scrivener. This could happen if the associated file is restored from a backup and one chooses to keep both copies, as a result of sync conflicts, or just manually duplicating formats as file on the disk.”

Interesting. I sure don’t think I did anything outside of Scrivener, but who knows? I’ll keep an eye on it.