I still think the trap with AC Voltage measurement should and can be addressed by changing the Default Sampling parameters to Auto when in AC Voltage mode.

This is difficult and addresses the complex question, how a user interface should work. Not every user want to see automatic intervention and changes of parameters, triggered by other actions. It’s possible, that a user want to have a fixed sampling rate when measuring AC. Another point is, what should happen with the sampling rate, when the user switches back from AC Voltage (stay or switch back)? Switch back means the former parameter must be stored (at the mooshimeter, not the app).