"Power quality" is one of those phrases that gets used to end a conversation. It should start one.
Voltage is a shape, not a number
A supply can measure a perfect 230V and still be hostile to the equipment connected to it. Distortion, dips and transients all live in the shape of the waveform, not its headline value.
Harmonics and the neutral problem
Modern loads — drives, LED drivers, IT power supplies — draw current in short pulses. Add enough of them on one distribution board and the third harmonic currents add in the neutral instead of cancelling.
The result is a neutral conductor carrying more current than anyone designed it for, running hot in a riser nobody looks at.
What measurement buys you
A week of logging gives you the evidence to size mitigation properly: filtering, a larger neutral, separating polluting loads onto their own board, or correcting the earthing arrangement.
Guessing at mitigation is expensive. Measuring it is not.