Two users are trying to access the temp files (where, for instance, the compiled templates are stored): www-data (when it's accessed from the website) and the sysadmin that run drush commands
By default, all these temporary files can only modified by the user that created it, so sometimes it's the sysadmin, sometimes it's the webserver user
Is there a way so all the temp files can be created/modified/deleted by only the admin user(s) and www-data?
One possible fix is a patch on drush, so it uses a separate templates_c folder than the one used by www-data. Could you test if it works in your environment/workflow?