Sir, running electronics (computer, modem, router, etc.) will screw with magnetically dampened beam scales if they're close together. If the electronics are turned off, they don't bother the scale, but I still prefer to use the scale several feet away from any electronics.
Some vacuum cleaners draw debris over or through the electric motor, which can be problematic if you're sucking up combustible things. (Think "sparks.") I've seen videos of vacuums blowing up from sucking up gasoline. The vacuums in the videos were floor-sweeper types rather than shop-vacs, though, and I understand that most shop-vacs do not draw the debris over the motor. I haven't personally tested this theory, but I still prefer a broom and dustpan.
The main thing with primers is not to put them in an airtight container such as a GI ammo can. I understand that an ammo can full of primers is basically a bomb if it gets hot enough, as in a house fire. I haven't tested this theory, either, but I keep my primers in a wooden cabinet with loose doors.
Hope this helps, and Semper Fi.
Ron H.