2 Problems: Google & Server Error

Pretty new to WP here so I’d appreciate your help.

First, Google Webmaster is giving off a bunch of crawl errors with 500 response code. It can’t fetch a handful of links. However, I tried the links they load just fine, which is baffling me.

So I checked error logs and so far I’ve found these. Not sure what they mean though (to note, footer.php loads fine in footer area).

PHP Fatal error: Call to undefined function ot_get_option() in /home/***/public_html/kb/wp-content/themes/wp-knowledge-base/footer.php on line 130, referer: https://www.google.ch/

Some example of links it’s giving off as 500 from Google but still load fine for me are

http://www.logicweb.com/kb/password-protect-directories/
http://www.logicweb.com/kb/install-lamp-stack-ubuntu-server/
http://www.logicweb.com/kb/tag/upgrade-kernel/