Mixed content issue while running updates.php in Drupal 6.37
Sorry, but I doubt this can be debugged from here. You need to:


inspect which elements, exactly, was served over HTTP instead of https.
Then, identify what created them (we may or may not be able to help)
Fix the reason - most common I know is hardcoding URLs in templates, but it might not be the case for you.


Last but not least, I find it to be much stable to use drush for updates.