When using the eye dropper to select the green screen in the Chromakey effect, the action is a bit jittery. Depending on where the dropper is placed could be the difference between selecting green or it may return 0,0,0,
I tried this during several days, reset the computer etc with the same results. It's not a hard failure since it will eventually select the proper color. I am using proper evenly lit green screen from tube tape.
Also, when I tested the same keyed footage with HF2U, it properly selected the color every time.