If I modify the example "Custom_Sensitivity" and move the carrier.begin() on line 22 and put it BEFORE line 20:
carrier.Button0.updateConfig(threshold);
it no longer respond to touch. However, if I uncomment line 16:
then it works again, even with carrier.begin(); before the setting.
I can not verify if the updateConfig actually change the values (yet) but I think the code should be robust to allow definition of button sensitivity before or after the begin.carrier() call.