Please see steps to reproduce as follows....

CREATE TABLE `a` (
`someField` VARCHAR(50) NULL DEFAULT NULL
)
COLLATE='utf8_general_ci'
ENGINE=InnoDB
;

/* This fails correctly with an INT conversion error (1292)

INSERT INTO A
WITH CTE AS (SELECT CAST(LTRIM(RTRIM('N/A')) AS INT) AS someNumber WHERE CAST(LTRIM(RTRIM('N/A')) AS INT) = 0)
SELECT 'blah' FROM CTE; */

/* but this runs okay with the CAST changing 'N/A' to a 0, only when you attempt any INSERT do you get an error

WITH CTE AS (SELECT CAST(LTRIM(RTRIM('N/A')) AS INT) AS someNumber WHERE CAST(LTRIM(RTRIM('N/A')) AS INT) = 0)
SELECT 'blah' FROM CTE; */

DROP TABLE A;

/* Which one is the preferred behavior? Can we get it consistent please! */