your two instances had different network horizons, because they were connected to different sets of ultrapeers. Think of the earth's northern hemisphere and the hemisphere east from the greenwich meridian to the date line -- there's a large chunk of overlap, plus some areas in only one hemisphere or the other, plus a chunk in neither. North America and much of the Pacific is in both; Asia is in only one; South America is in the other; Australia isn't in either. Europe and Antarctica are divided east-west, the Atlantic is divided north-south, etc...