Bike cadence sensor issue

I've just got a garmin cadence sensor. Easily paired with my f5x. Rotating the crank the cadence is normally sent to fenix and recorded. The strange thing is that when I stop rotating the crank, the RPM reported on screen remains stuck on last measurement and doesn't go to zero. Tried with 920xt and the behaviour is correct. Tried on f5x with fw 9.02 e 9.10 and the issue is the same. Someone has reported the same behaviour?