Multiple errors after upgrading to 4.7.21 and Joomla 3.7.3
This was caused by [civicrm.root] using
https://www.mydomain.com/components/com_civicrm/civicrm/

while it should be using
http://www.example.com/administrator/components/com_civicrm/civicrm/

The $civicrm_root variable is correct in both civicrm.settings.php files so I'm really confused why CiviCRM cannot pull the civicrm.root variable correctly.