Feels a bit like groundhog day, but here goes . . . Scales can be affected by air currents, static electricity, and (for electronic scales) both line and transmitted (RF) "noise".
While air currents and static electricity can affect any scale weighing the small quantities reloaders care about, they are relatively easy to counter whether your scale is beam or electronic. "Noise" will not affect beam scales.
All electronic scales under ~$500 use the same base technology, ie, strain gauge load cells. Unfortunately these are very susceptible to "noise", often being sarcastically referred to as "noise gauges". Noise can come over the line or OTA from many sources . . . anything that transmits (cell phones, wireless phones, WiFia), motors, fluorescent lights and ballasts, microwaves and more. These scales interpret noise as changes in weight.
Scales above this price point begin to use different technologies, eg, magnetic force restoration. Such scales are not susceptible to noise. [The lowest priced scale I and others have seen while watching many reloading forums is the A&D FX120i which can be had from Cambridge Environmental for ~$5XX depending on the Canadian exchange rate.]
Some people claim their digital scales are rock stable and accurate. While that may be true for them, it may be that their reloading room is relatively noise-free. Apparently your room is not noise free.
So it is unlikely that any sub-$5XX digital scale is going to behave any differently in your room . . . regardless of line filters, UPSs, or battery power if your noise is RF . . . than the one you have.
That's what happened to me until my A&D FX120i became my 7th scale. I also added devices called AutoTrickler and AutoThrower (you can google them) that converts the A&D to a Chargemaster that really works in any room.
BTW, I kept my beam scale for backup.