[N5GKP]

So, if you can access the instrument cluster secret menu set it to the voltage screen.
Go for another drive and watch the voltage, when you accelerate does the voltage sporadically drop to around 12.3-12.6V? And then brake and see if it returns to 14V+,
If thats whats happening id be happy to say I don't see it as an issue. 'Smart' alternators tend to switch on and off quite often when driving, for efficiency's sake BMW have tried to work it so when the engine is under load, unless necessary the alternator will briefly turn off and then turn back on when on overrun / deceleration.