This along with the 737max are examples of overtly complicated designs, to the extent that they are affected in more ways than simpler designs. What I believe you are experiencing is the effect of the phones radiation on the sampling clock which times the scale's sample rate and/or the power supply noise. For those that gave up their cable bill and use an antenna, go next to you antenna and make a cell call... you'll see this effect. In any case, I don't think a power conditioner would improve the situation and proof would be if you still see this when battery powered, if possible. Great catch, though, to identify the source!