That just looks like you need practice. The common misconception of Steadicam systems is that they just work out of the box. If you search through the forums, you will see this thread being brought up again and again. All I can say to you, is that you need to practice, take some lessons, read, etc. I hope this helps.
Thanks for your help Mr. Rencher, in our local forum, newbies post also keep repeating, however not many wish to share the technique.
It is weird that if I run instead of walk when using merlin, bouncing up and down with foot step will somehow smaller.
Anyway, nice to meet you, and thank you very much.