TopMarginPercent in PercentRelativeLayout behaves strangely in nested Views

Question

I am using PercentRelativeLayout for positioning a view on an image. However, it seems like that marginTopPercent always depends on the height of the entire view even if the height of my PercentRelativeView is smaller. How can I make it dependent on the height of my RelativeLayout? MarginLeftPercent does work fine tho.

Code:

  <?xml version="1.0" encoding="utf-8"?>
<android.support.percent.PercentRelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:layout_width="match_parent"
    android:orientation="vertical"
    android:layout_height="match_parent"
    >

    <android.support.percent.PercentRelativeLayout
        android:layout_marginTop="50dp"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentStart="true"
        android:layout_alignParentTop="true"
        android:orientation="vertical">


        <ImageView
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentStart="true"
            android:layout_alignParentTop="true"
            android:adjustViewBounds="true"
            android:scaleType="centerCrop"
            app:srcCompat="@drawable/apparea" />

        <com.petarzoric.vr_feedback.PaintView
            android:id="@+id/idk"
            android:layout_alignParentStart="true"
            android:layout_alignParentTop="true"
            android:layout_marginStart="40dp"
            app:layout_aspectRatio="300%"
            app:layout_marginLeftPercent="2.6%"
            app:layout_marginTopPercent="50.65%"
            app:layout_widthPercent="84.13%" />

    </android.support.percent.PercentRelativeLayout>



    <Button
        android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_alignParentStart="true"
        android:layout_marginBottom="75dp"
        android:layout_marginStart="146dp"
        android:text="Button" />


</android.support.percent.PercentRelativeLayout>

As you can see the parent view wraps the content. The topMarginPercent is set to 50%, but the image cleary shows, that it is more than 50% of the parent. It is 50% of the entire height of the view. How can I solve this?

Thanks in advance.