I have completed tests that I can access via xmlResult but not jsonResult.php.
/xmlResult/{testid}/ - 200, test data available
/jsonResult.php?id={testid} - 400, test data not available
When I login jsonResult seems to work, but clearing cookies causes the 400 error to come back.
I looked into the .htaccess file and see that xmlResult.php is redirected from /xmlResult/. Doing the same for jsonResult.php has fixed my problems with 400 returns.