In all honesty, it sounds like two things.
1) it sounds like the NVR has a problem. Maybe a bug from an update. Maybe a surge messed it up. I can't see a RF causing the "view" to change. And if it is isolated (truly air-gapped) then he can't change it via hacking.
2) there could also be some RF issue you are finding but should not be affecting ONLY your NVR.
As far as the RF, and you think it's your neighbor causing it, it is probably also affecting your neighbor and anyone else within range (not just you). If it's the coil it will be broadcast not a beam aimed at you (can't think of better words at the moment).
If your reading device has a logging capabilities use them. How long do the high readings last? A few seconds, a few minutes, an hour? Also how often? Is there any pattern when they go up?
If they go on for a few minutes or longer and you want to be sure once and for all it's your neighbor, turn off the main in your electrical panel when the readings are high. If they drop after you turn off the main then it's probably NOT your neighbor. Granted they will drop a little from your load but if your neighbor REALLY is doing something they will still be elevated. Then before turning your main back on, turn off all the individual circuits. Turn the main back on with all the circuits off. Turn one circuit on at a time to see which circuit is causing the problem. Then look at the items on the circuit. Etc.
Also keep in mind that although you didn't change anything in your home some animals may have. For example, just helped a neighbor fix his A/C and when I opened the condenser unit it looked like a mouse made a home in their over the winter. After clearing out all the debris I found many wires were chewed and had to be replaced.
One more thing, do you live near power lines? Any new construction in the neighborhood?