When I use the [upcoming-services] shortcode on a post page, it produces a server error. Warning: Cannot modify header information - headers already sent by (output started at /home/uuclcadmin/uuchurchlc.org/wp-content/plugins/uua-services/inc/upcoming-services-shortcode.php:27) in /home/uuclcadmin/uuchurchlc.org/wp-includes/pluggable.php on line 1216. Both the UUA WordPrese theme and the UUA services plugin are the most recent versions.