Seaquel
SQL Server error code

SQL Server error 6815

SQL Server raises error 6815 at severity 16, which marks a problem with the query or data that you can correct.

In the FOR XML EXPLICIT clause, ID, IDREF, IDREFS, NMTOKEN, and NMTOKENS attributes cannot be hidden in '%.*ls'.
Msg6815
Severity16
Group6000–6999

Source: Database Engine events and errors