Windows 7 network performance monitor inconsistency

I am doing a backup using disk2vhd from former sysinternals (now Microsoft) Mark Russinovich and I’ve found something puzzling.
The source is a W7 ultimate machine, the destination is a SMB share on a W7Pro connected to the same 1Gb/s Ethernet switch.
The two systems are not doing any other significant network activity but I see resource monitor reporting very different network use on the two sides of the transfer.

I am monitoring the destination machine from the source machine using teamviewer (great tool free for personal use) and here is the picture of the two paired resource monitors:
networkuse
The source machine (on the right side) reports a network use that is significantly lower than the destination machine (on the left side).
The source machine also shows that the largest transfer alone (the backup) has a higher throughput than the total reported.

I was thinking the discrepancy might be related to a time drift in the reporting, but the graphs show that is not the case: the destination system constantly reports a higher network use.
Does anyone know if it is a known bug in W7 and how to fix it?

Dell 6430u updated to bios A10

Two days ago I did a new bios update on the notebook.

The process worked fine as usual and, again as usual, did not fix or improve the issue with the fan noise.
After 36 months with it I have to bear it for only 12 more months until the notebook is due to refresh.

A positive note about the 6430U: it does no longer trigger the security scanner in the Ben Gurion airport. Whatever the chemical that was there it is now completely evaporated.