I have similar observation with my other brand SDR. (Elad FDM-S1, SDRPlay rsp 2)
I have two monitors connected to my Lenovo notebook. Sometimes the picture displayed on the second screen affects the reception noise “spikes”) on the SDR. I had thought that LCD monitor creates some RFI, but switching off this monitor did not help.
It also differ depends on antenna type and frequency... One day I have “spikes” the other day they are gone with the same setup. (????)
Maybe to add bunch of the ferrite clamps to the monitor cable could help, but I haven’t found time to verify it yet.
Please continue with your lab tests :-)