Some node contacts us before we are able to properly handle their gossip.
This can be of two forms:
They send us communication but their latest gossip event betrays that we are not in their routing table (AddPeer(Us) was not consensused as far as they know)
Note: this covers this particular case:
They send us communication where the initial gossip event is followed by an Event with Cause::Response before an Event with Cause::Request
This allows for events with Cause::Observation to be added, but the Request/Response pattern to be good enough to prove non-spammy behaviour