Once upon a time, the uplink was sending a message to the storage node before closing the channel. That is an additional roundtrip. For faster downloads, the uplink nowadays just terminates the connection without any hint. The storage node is forced to guess and will produce different messages depending on the situation in which this happens. Most of the time the storage node will assume the reason was the longtail cancelation but in some rare cases, it can also produce other error messages.