Olympe video streaming from Bebop2 fails due to "invalid stream socket err"

Product: [Bebop/Bebop2]
OS: Ubuntu 18.04.3
Olympe: Installed last week, so it should be latest

I am trying to get the video stream from “Bebop 2 Power” using Olympe sample program ‘streaming.py’.
But it fails due to (I guess) the following errors:
E pdraw_dmxstrmnet: getSingleStreamLocalStreamPort:231: invalid stream socket err=71(Protocol error)
E pdraw_dmxstrmnet: getSingleStreamLocalControlPort:246: invalid control socket err=71(Protocol error)

The connection to Bebop 2 seems OK because I could take-off and land the drone.
Could someone give me advises to fix the issue?

Sincerely,
Hiro