Seaquel
SQL Server error code

SQL Server error 6850

SQL Server raises error 6850 at severity 16, which marks a problem with the query or data that you can correct.

%.*ls name '%.*ls' contains an invalid XML identifier as required by FOR XML; '%c'(0x%04X) is the first character at fault.
Msg6850
Severity16
Group6000–6999

Source: Database Engine events and errors