An abnormality in the power quality that is being delivered to a system is often referred to as "dirty power." Abnormalities can include low power factor, frequency variations, voltage variations, and surges/spikes.
A more likely feature of 'dirty power' would be electronic noise or interference frequencies superimposed on the line voltage. These could be caused by faults in the power source generating circuits. The thing is; the line voltage and frequency might be perfectly correct, but if it has noise on it, (which an avionics engineer would be able to see on an oscilloscope), a digital system can get confused because noise can appear to be a random series of Ones and Zeros.
Having said that, I have never known this problem, but I have seen the power transfer from external power to APU, (or vice versa), sometimes cause faults in some systems.