After a topic is deleted, if the topic has a parent topic, you are supposed to be led to the parent topic. But you are led to WebHome at times. This happens if the parent topic's name is not a wikiword.
This happens because the redirect destination is determined after a topic is moved to the trash (= deleted) and the logic to determine the parent topic depends on the parent topic is renamed to Web.Topic from Topic. If the name of a deleted topic is not a wikiword, the link conversion from Topic to Web.Topic does not happen.
This bug can be easily fixed by making the actual topic move happen after determining the URL destination.