If listeners are updated as part of a configuration update then the pushAll method will push out old routes to the envoy proxy. The envoy proxy may respond with a request for an update which acks the invalid request (nonce, version are correct) but contains different routes.

In one test we had a race where we could either have a successful transition from listener/route A -> [] -> B or an unsuccessful transition from listener/route A -> B however this would also occur when transitioning from A -> A,B and A,B -> B.