We’re having an issue on several sites with site url links from structure and encoding of the fancy brackets.  Here is the modification we made to the ext.wyvern.php file if its helpful for anyone else:

Line 207

It wont respect the preg_match on line 221 - so here it is in plain text:

preg_match_all(”/{page_url:(d+)}|{;page_url:(d+)};/”, $tagdata, $matches); 

(the double semi-colon is actually a forward slash, then a semi-colon)

function channel_entries_tagdata_end($tagdata, $row, $instance)
    {
        if($this->parse_order == 'early')
        {
            log_message('debug', 'Wyvern: Parsing {page_url:N} variables - channel_entries_tagdata_end - line 193 ext.wyvern.php');
            
            // has this hook already been called?
            if ($this->EE->extensions->last_call)
            {
                $tagdata = $this->EE->extensions->last_call;
            }
            
            preg_match_all("/{page_url:(d+)}|{;page_url:(d+)};/", $tagdata, $matches);

            if(count($matches) > 0)
            {
                foreach($matches[1] as $match => $mval)
                {
                    // If the page ID exists, replace the tag accordingly
                    if(isset($this->EE->config->_global_vars['page_url:'.$mval]))
                    {
                        $tagdata = preg_replace("/{page_url:$mval}/", $this->EE->config->_global_vars['page_url:'.$mval], $tagdata);
                    }
                    // If not, then replace the tag with a blank string, we don't want the tag itself to be rendered
                    else
                    {
                        $tagdata = preg_replace("/{page_url:$mval}/", '', $tagdata);
                    }
                }

                foreach($matches[2] as $match => $mval)
                {
                    // If the page ID exists, replace the tag accordingly
                    if(isset($this->EE->config->_global_vars['page_url:'.$mval]))
                    {
                        $tagdata = preg_replace("/{;page_url:$mval};/", $this->EE->config->_global_vars['page_url:'.$mval], $tagdata);
                    }
                    // If not, then replace the tag with a blank string, we don't want the tag itself to be rendered
                    else
                    {
                        $tagdata = preg_replace("/{;page_url:$mval};/", '', $tagdata);
                    }
                }
            }
        }
        // $tagdata = "";
        
        return $tagdata;
    }