I encountered the same error, this is the bug in co-authors plugin.
There is a quick fix for it:
Search for function posts_where_filter() in co-author-plus.php and then search for line
$where = preg_replace( '/(\b(?:' . $wpdb->posts . '\.)?post_author\s*=\s*(' . get_current_user_id() . '))/', $current_user_query, $where, -1 ); #' . $wpdb->postmeta . '.meta_id IS NOT NULL AND
near the end of this function
You should replace it with
$where = preg_replace( '/(\b(?:' . $wpdb->posts . '\.)?post_author\s*=\s*(' . get_current_user_id() . ')\b)/', $current_user_query, $where, -1 ); #' . $wpdb->postmeta . '.meta_id IS NOT NULL AND
I added \b to only match on word boundaries. Previously it matched current user id as a substring of post_author id and that caused problems.