I was wondering which type of power adaptor the Smart Hub is using. If it's using a "series mode" regulator, then this may be one reason for the HH6 very stable operation. i.e. the Noise Margins appear to be very stable (assuming that the diagnostics display is correct. Margin does change sometimes, though).
One of the previous Hubs (HH3) was boasting a switch mode regulator power adaptor - it's more efficient!
Yes it's more efficient but it's a real mean machine in it's near-field emissions.
Hope that the new supply has reverted to series regulation. It wastes more heat, but there's much less electromagnetic field noise.
This is the reason why it's better to use any new edition Hub with it's own supply.
Some manufacturers are selling substitute power supplies and UPS's. These would need very careful examination.