How to remove the black background from the button?

Question

Android

The essence of the problem is that it is not clear why the buttons have a black background. I've seen this before on some devices in the "play market" application.
How it is displayed on my device (4.4.2):

How it is displayed on another device (4.2.2):

Here is a piece of xml responsible for the buttons:

<LinearLayout android:orientation="horizontal" android:layout_width="fill_parent" android:layout_height="wrap_content">
            <ImageButton android:id="@id/advanced_button" android:layout_width="wrap_content" android:layout_height="32dp"  android:paddingRight="8.0dip" android:paddingLeft="4.0dip" style="?right_separator" android:layout_marginTop="4dp" android:layout_marginBottom="4dp" android:src="@drawable/btn_show_post_panel" />

            <Button android:id="@id/btnAttachments" android:paddingRight="8.0dip" android:paddingLeft="8.0dip" style="?right_separator" android:layout_width="wrap_content" android:layout_height="32dp" android:text="0" android:layout_marginRight="4dp" android:layout_centerVertical="true" android:drawableLeft="@drawable/ic_menu_attachment" android:textColor="#ff9D9D9D" />

            <Button android:id="@id/btnSendPost" style="?btnsend" android:layout_width="fill_parent" android:layout_height="40dp" android:text="Отправить" android:textColor="#ffffffff"/>
</LinearLayout>

Here is the right_separaor:

<layer-list
  xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:top="-3px" android:bottom="-3px" android:left="-3px">
        <shape android:shape="rectangle">
            <stroke android:width="3px" android:color="@color/right_separator_color_bl" />
        </shape>
    </item>
</layer-list>

In principle, there are suggestions that it could be and where to dig, but suddenly someone has already encountered this and can tell you what needs to be done.

Answer 1

As expected, I solved it by adding a line
In right_separator.