I cannot demonstrate this on a video. However, if a team-mate tries to ping a location on a map, it is not possible to see the ping. What good is a ping if you can't see it? None
This has happened once when I was playing with FelixTCat over the weekend. He was unable to ping me in one of our games.
I don't know if this has been posted before or if it's even well known but yeah, that happens. We also can't see each other's feud of view which I desperately hope will be implemented in the future...