JSON_VALUE broken in functions

We have found a serious problem with JSON_VALUE which apparently was partially fixed in 10.2.16. Specifically we're extracting a Date from JSON and if that extraction is in a function it does not work.

ERROR: Truncated incorrect datetime value: '2018-07-26T00:00:00+03:00'

If the extraction is done from the query (ie no function that does it) then it works fine.

Please see the following example:

SET NAMES 'utf8';

USE import;

DELIMITER $$

CREATE DEFINER = 'jsupport'@'10.8.0.%'

FUNCTION J_SON ()

RETURNS date

BEGIN

  RETURN (SELECT

      date (JSON_VALUE('{"b":"2018-07-26T00:00:00+03:00"}', '$.b')));

END

$$

DELIMITER ;

-- WORKING -> SELECT date (JSON_VALUE('{"b":"2018-07-26T00:00:00+03:00"}', '$.b'));

-- BROKEN    -> SELECT J_SON();