Steps to reproduce the issue

• I am using WordPress 4.7.1 with a custom theme;
• I have Jetpack 4.5 enabled with Development Mode via the JETPACK_DEV_DEBUG constant;
• I created a page with a Jetpack/Grunion contact from;
• I sent a message via this page;
• I received the message in my inbox.

What I expected

• Message would be sent and I could see the success message on my browser

What happened instead

I see the following on my browser:

Warning: print_r() has been disabled for security reasons in plugins/jetpack/modules/contact-form/grunion-contact-form.php on line 2043

Warning: Cannot modify header information - headers already sent by (output started at plugins/jetpack/modules/contact-form/grunion-contact-form.php:2043) in wp-includes/pluggable.php on line 1179