Why is elevation so difficult ?

I started out with a very exact elevation and climbed 700 meters. Then Venu3 thought I had a problem and sent out an emergency message. This also stopped the recording of my trip.

No worries. I just started a new trip - BUT now (60 seconds later) Venu3 thought I was 200 meters lower (on 500 meter). HOW COME ?

Is the Venu3 not barometric ? Should it not have the same elevation within 60 seconds ?