My Vuforia Objects don't stand still

First, please check this video out  https://youtu.be/OycbIH5A7E8

I'm making an AR-based application with Unity 2018.2.3f1

As you see this video, AR objects(stars) keeps moving.

I added 9 stars on my marker image.

But when Vuforia recognize my marker, AR objects(star) don't stand still.

I guess the problem is caused by the empty area in my marker.

In my marker image, center area is empty(with white color).

But in real environment, there are 9 cubes inside the marker.

How can I solve this problem?

If you need more further information, please let me know.

I'll add more information on my thread.