What does "Visit Waypoint" in missions mean?

The new "Missions" feature has some mission steps called "Visit Waypoint". What does that mean? How do you visit waypoints?

I've tried a mission yesterday and couldn't clearly figure out what it meant. Some waypoints were completed automatically in a few seconds after walking into the waypoints but some didn't. I had to press on the waypoint markers and open the linked Fieldtrip page to complete them and one of them even reacted more strangely: I had to select the waypoint marker and press on "Navigate" to finally complete it.