ARRAY_EXCEPT() returns wrong results

SELECT RAW c FROM 1 AS d UNNEST ARRAY_EXCEPT([1,2,3,4,5],[2,4]) AS c;

[1,3,5,null,null] vs [1,3,5]

 SELECT ARRAY_EXCEPT([1,2,3,4,5],[2,4]) ;

returns [1,3,5]

WITH o AS ([2,4]) 

SELECT RAW  c 

FROM [{"a":[1,2,3,4,5]}] AS d 

UNNEST ARRAY_EXCEPT(d.a,o) AS c;