Hello. Yes your fix does appear to be working!I can see the post on Chrome and Safari.
Yes, you can update the parent theme on the staging site.
Thanks.
I am thinking this may be causing the issue: Avia_Popup_Templates::get_border_styles_options() in /var/www/wp-content/themes/enfold/config-templatebuilder/avia-shortcodes/columns/columns.php:561
Thanks, Guenni007, that worked for me, too.