Seaquel
SQL Server error code

SQL Server error 6840

SQL Server raises error 6840 at severity 16, which marks a problem with the query or data that you can correct.

Neither XMLDATA nor XMLSCHEMA supports namespace elements or attributes such as '%.*ls'. Run the SELECT FOR XML statement without it or remove the namespace prefix declaration.
Msg6840
Severity16
Group6000–6999

Source: Database Engine events and errors