Featured Content bug?

There's a couple of issues: 1) When I add text to a 'Content' box in the Customise / Featured Content section I get the following error repeated several times at the top of the homepage preview: Warning: call_user_func_array() expects parameter 1 to be a valid callback, function 'wp_kses_post;' not found or invalid function name in /home2/louise/public_html/wp-includes/plugin.php on line 213 And I basically can't add text to featured content this way. 2) When I use the Theme Options / Featured Content I can add text to the Content boxes for all three Featured Content items with no error messages, but only the first one appears on the Home page. When I add text this way it appears in the Customise / Featured Content previewed home page correctly, but not in the actual home page that visitors would see. The webpages in question are currently under construction and can be found at http://greystoneskittyhostel.com/ I am using the free version of the theme and Wordpress 4.3. The only active plugins I currently have are Akismet, Yeost SEO, Regenerate Thumbnails and Jetpack. The site is hosted, rather than the free .wordpress.com version. I'm setting it up for a fellow animal welfare organisation. I've a coding background years ago - these days I'm an informed amateur using Wordpress on a need-to-know basis. I nearly abandoned using this lovely theme last night when, after having this problem, no changes I made in customisation were reflected on the home page. I uninstalled as a result. This morning after reboot I reinstalled to try again as I really like the theme, and everything worked okay. I've just tried the Featured Content again for the first time just now and same problem has occurred. Any solution appreciated! Tis a lovely theme - thanks for making it available, and I'll use it without the Featured Content text if need be. Thanks! Muriel