Seaquel
SQL Server error code

SQL Server error 9538

SQL Server raises error 9538 at severity 16, which marks a problem with the query or data that you can correct.

Paths with same path expression indexed with selective XML index '%.*ls' should have SINGLETON option either specified for all of them or for none of them.
Msg9538
Severity16
Group9000–9999

Source: Database Engine events and errors