For the audio (Tia’s) problem, (“Hey Google” doesn’t produce any result) I suppose it is possibly or even likely the same problem as described and commented in this very long topic:
The work-around for that problem is to turn off the Google Assistant!
This problem is one of the known problems of the FP4 as catalogued here. It only affects certain units.
Tia and Owein, another question: are the people you call, experiencing problems hearing you?