Venu 3 does not stop recording when training ends?

I have just upgraded from my trustworthy Forerunner 235 to a Venu 3.

On my Forerunner, I mostly used a simple training called "Run 5 kilometers" and the watch would automatically stop recording the activity at the very moment I reached the 5 kilometers - and of course also give a sound and a visual warning. 

It seems like the Venu 3 gives the warnings, but does not stop the activity when the goal is reached, which is really annoying since I am having a tough competition with myself where every second counts. I have tried to stop it manually, but I always miss a few precious seconds and it takes focus from my final pitch.

Am I missing a setting somewhere? 

Thanks!