The disconnect specs read the tick count right after the client destroyed its socket, but the server only sees the disconnect once the socket close reaches it. Under load the producer's 20 ms interval could tick once more in between, so the count was off by one (7 of 12 runs failed under full CPU load).
The producer now records its teardown, and the specs take the count once it has happened. They still fail when the producer is never stopped.
Kamil Myśliwiec
67a255e09d