That’s really weird. The topic URL is generated by bbpnns (not any of the add-ons) using this line of code:
$url = apply_filters( 'bbpnns_topic_url', bbp_get_topic_permalink( $post_id ), $post_id, $title );
As you can see, it will use whatever bbPress returns as the topic permalink, and pass it through the
bbpnns_topic_url filter, which may not even exist.
You should check your database for instances of the IP to see why this would be happening.