Try this
In your theme functions.php find this:
add_filter('post_gallery', 'my_post_gallery', 10, 2);
comment that out and replace and add this to it:
<strong>if( !is_admin() )</strong> add_filter('post_gallery', 'my_post_gallery', 10, 2);
This was fixed in this ticket https://github.com/Automattic/facebook-instant-articles-wp/issues/116
Here is the commit in the file “fb-instant-articles/class-instant-articles-post.php” line 666 just and else to fix encoding
else {
$content = htmlspecialchars_decode( utf8_decode( htmlentities( $content, ENT_COMPAT, 'utf-8', false ) ) );
}
https://github.com/Automattic/facebook-instant-articles-wp/commit/4ab869bcf907119b3aa18f95e5efec389f418ba1
I was having the same problem and this fix it, hope they add it in the next update of this plugin.
Thanks to the developers and the guy how fix it!
