AR app only shows the center of the object

Good morning,

I made an AR Project in Unity with Vuforia. The aim is to show a sailboat. Therfore we defined the target (the hull of the boat). Our AR-app is recognizing this target.
In the next step we fade in different parts, like the focks and the different sails. But when we push the butten to fade in this parts. The AR app shows the center of the boat. So we can not see the different parts because we are staying inside the middle of the boat.
Attached you can find the screen of our app when the target is recognized. In the second picture you see the screen, when we fade in a part and the app is moving to the center of the boat

We have no idea, what our problem is. Is it something in the settings of the AR camera? The app should only fade in this part in the same position like the target is shown.

It would be nice when somebody can help us.

Thank you and best regards.