I consulted once for a hospital that was experience seemingly random network outages. After a few questions with the staff there it seemed to happen whenever a person stepped away from their windows (Lenovo) workstations for too long. Say, after lunch or breaks. After a wireshark of the network I determined it was a network card driver that was causing a broadcast flood on the network from multiple points for stations with the same driver version. While not the fault of Windows (I dont think anyways, as an update of the driver fixed the issue) your comment did remind me of this experience.