My domain admins can't modify self created aliases. Postfixadmin quits with following message:
Check config.inc.php - domain administrators do not have the ability to edit user's aliases (alias_control_admin)
The error message already gives you a hint - set $CONF[alias_control_admin] to YES if you want to edit mailbox aliases as domain admin.
Does it work with this config change?
As written above some months ago, this looks like a configuration issue.
Please reopen if the problem still exists after changing the configuration.