Oracle Message ORA-19148 - XQST0090: It is a static error if a character reference does not identify a valid character in the version of XML that is in use

ERRORXQST0090: It is a static error if a character reference does not identify a valid character in the version of XML that is in use
CAUSEAn error occurred during the processing of the XQuery expression.
ACTIONCheck the detailed error message for the possible causes.