There are multiple versions of records in the srs_marctab table in the CUL LDP. The correct version is called ACTUAL. Here is an example of how you might specify getting the ACTUAL version.
language_extract AS (
SELECT
sm.instance_id AS instance_id,
substring(sm.content, 36,3) AS LANGUAGE,
sr.state,
sr.id
FROM srs_marctab AS sm
LEFT JOIN srs_records AS sr on sr.id = sm.srs_id
WHERE
sm.field = '008'
AND sr.state = 'ACTUAL'