When I enable a Upfront theme, I got this error on the admin dashboard:
Warning: Cannot modify header information - headers already sent by (output started at /wp-content/plugins/zen-menu-logic/zen-menu-logic.php:126) in /wp-includes/pluggable.php on line 1216
This only happens when an Upfront theme(it doesn't matter which Upfront theme) is enabled, swapping to the default WordPress, the error gone.