Seaquel
SQL Server error code

SQL Server error 3056

SQL Server raises error 3056 at severity 16, which marks a problem with the query or data that you can correct.

The backup operation has detected an unexpected file in a FILESTREAM container. The backup operation will continue and include file '%ls'.
Msg3056
NameDMPDB_INVALID_FSDATA
Severity16
Group3000–3999

What it means

Error 3056 is raised if files exist under the FILESTREAM container (folder) that aren't created by SQL Server. The backup operation will include that file, but this will cause an inconsistent state of the filestream components in the database.

Source: Database Engine events and errors