ORA-00911: invalid character

[ERROR] Failed TO EXECUTE goal org.liquibase:liquibase-maven-plugin:3.2.0:UPDATE (update-rice) ON project kfs-data: Error setting up OR running Liquibase: Migration failed FOR change SET liquibase/rice/data.xml::NWUKFS-2724::za-kfs:
[ERROR] Reason: liquibase.EXCEPTION.DatabaseException: Error executing SQL DELETE FROM FP_SEQUENCE_T WHERE DOC_TYP = 'KREW_DOC_HDR_S';
[ERROR] DECLARE
[ERROR] max_sequence_value INTEGER;
[ERROR] BEGIN
[ERROR] SELECT NVL(MAX(TO_NUMBER(DOC_HDR_ID)), 1) + 1
[ERROR] INTO max_sequence_value
[ERROR] FROM KREW_DOC_HDR_T;
[ERROR] EXECUTE IMMEDIATE 'insert into FP_SEQUENCE_T (DOC_TYP, NEXT_SEQ_NBR, VER_NBR) values (''KREW_DOC_HDR_S'', '  || max_sequence_value || ' , 1)' ;
[ERROR] END;: ORA-00911: invalid character
[ERROR] -> [Help 1]