Invalid value on valueset

Summary:

Invalid value on valueset

Content (please ensure you mask any confidential information):

This is my valueset:

The code is:

FROM:

(SELECT to_number(ID) ID, VALUE NAME, REGEXP_SUBSTR(DESCRIPTION, '(([^)]+))', 1, 1, NULL, 1) DESCRIPTION, 2 SORT FROM PER_PERSON_LIST_V UNION SELECT -1, 'N/A' NAME, 'N/A', 1 SORT FROM DUAL) A

WHERE:
1=1 AND (A.ID = -1 OR EXISTS (SELECT 1 FROM PER_PERIODS_OF_SERVICE POS WHERE to_char(POS.PERSON_ID) = A.ID AND POS.ACTUAL_TERMINATION_DATE IS NULL))

Why do I have this error?

Note: somehow it seems related to different people having the same name, anyway the Person Number should be enough to distinguish