I have had the same braking problem with my 2016 Versa S with 5 speed. So I don't think it's the CVT doing it. I agree with the OP that it's the A/C that's doing it. I have experienced this 3 times since I bought my car new in Oct 2016. All 3 times the A/C was on. My pedal also went nearly to the floor when it happened. Dealer of course can not reproduce the problem.