HTTP 500 Error

Hi
I keep on getting a HTTP 500 Error and my error Log is pointing to your plugin.

Why is it doing this? At the moment I have deactivated the plugin.

These are some of the errors below:

towywebdesigns.uk [Tue Jan 09 17:24:50 2018] [error] [client 2.99.188.115:49866] PHP Fatal error: Uncaught Error: Call to undefined function insert_with_markers() in /home/sites/1b/9/9f4e57b2bc/public_html/towyvalley/wp-content/plugins/http-headers/http-headers.php:1044

towywebdesigns.uk [Tue Jan 09 17:24:50 2018] [error] [client 2.99.188.115:49866] #0 /home/sites/1b/9/9f4e57b2bc/public_html/towyvalley/wp-content/plugins/http-headers/http-headers.php(642): update_headers_directives()

Cheers

Colin

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