Some CSS elements of video portal chat has been misfit.
1.- Login as instructor and as student of the same site in another browser/session.
2.- In the shared site go to the overview page (with multiple tools on it)
3.- Now you can see the other user in the chat window, open a dialog window by clicking in user's name.
4.- Then reduce the browser window to allow you check that if the chat window is over one tool title the title is behind the chat window.
5.- Try to start a video call and check that the connection established message is not visible.
See the screenshot for a better understanding.