If you use the Eventcalendar Plugin in WordPress you may experience duplicated or even more searchresults if a blogpost is in more than one category. To get rid of this problem change the following in eventcalendar3.php:
function ‚ec3_filter_posts_where‘ add the following to the first if statement
|| $wp_query->is_search
It should look like this afterwards:
if($wp_query->is_page || $wp_query->is_single || $wp_query->is_search )