Layout Editor (Design) changes properties of random views when changing another one's

I'm having a strange problem when editing a property of a view inside the layout editor that happened before but it seems it got worst updating from 0.8.6 to 0.8.9.

I have two activities named activity_main and activity_item, inside I have two totally unrelated ImageButtons well, they are both image buttons and both have a drawable as background. When I created the drawable for the second imagebutton i copied it from the first one.

This is the code for the first ImageButton (The one inside activity_main):

<ImageButton
                android:layout_width="60dp"
                android:layout_height="60dp"
                android:id="@+id/btExpressRoute"
                android:layout_gravity="center_horizontal|top"
                android:background="@drawable/button_express" />

And this is the code for the second one:

<ImageButton
        android:layout_width="60dp"
        android:layout_height="60dp"
        android:id="@+id/btStar"
        android:background="@drawable/button_star"
        android:layout_alignParentTop="true"
        android:layout_alignParentRight="true"
        android:layout_alignParentEnd="true"
        android:layout_marginRight="10dp"
        android:layout_marginTop="10dp" />

Ok, the problem is this one: IF i change the background for the second imagebutton from the design editor the first background gets changed accordingly. It's like if those two properties were linked! If i make the change from XML this does not happen.

I should also add that my project is under git control.

Do you have any clue about how to avoid this? (Except that i should only use XML :))