Constraint Layout TextView Overlap

I'm having some issues inside a constraint layout where i have a TextView which supports multiple lines. When the TextView is expanded it overlaps with other components inside the constraint layout. Below is the XML layout that i'm using and a GIF to demonstrate.

Any help would be much appreciated.

Demonstration -> https://puu.sh/xPFSF/3f6711a68f.gif

<ScrollView xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:background="@color/activity_background"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:fillViewport="true">

<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:focusableInTouchMode="true"
    android:layout_height="0dp">

    <android.support.constraint.Guideline
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/leftGuideline"
        app:layout_constraintGuide_begin="20dp"
        android:orientation="vertical"/>

    <android.support.constraint.Guideline
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/rightGuideline"
        app:layout_constraintGuide_end="20dp"
        android:orientation="vertical"/>

    <TextView
        android:id="@+id/subject"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="@string/subject"
        android:layout_marginTop="20dp"
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="@id/leftGuideline"
        app:layout_constraintEnd_toEndOf="@id/rightGuideline" />

    <EditText
        android:id="@+id/message"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:hint="@string/your_message"
        android:layout_marginTop="20dp"
        android:minLines="2"
        app:layout_constraintTop_toBottomOf="@id/subject"
        app:layout_constraintStart_toStartOf="@id/leftGuideline"
        app:layout_constraintEnd_toEndOf="@id/rightGuideline" />

    <Button
        android:id="@+id/sendMessageButton"
        android:layout_width="0dp"
        android:layout_height="wrap_content"
        android:layout_marginTop="20dp"
        android:text="@string/send_message"
        style="@style/button_main"
        app:layout_constraintVertical_bias="1"
        app:layout_constraintTop_toBottomOf="@id/message"
        app:layout_constraintStart_toStartOf="@id/leftGuideline"
        app:layout_constraintBottom_toTopOf="@+id/saveDraftButton"
        app:layout_constraintEnd_toEndOf="@id/rightGuideline" />

    <TextView
        android:id="@+id/saveDraftButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/save_draft"
        android:layout_marginBottom="10dp"
        android:drawableStart="@drawable/icon_arrow"
        android:gravity="center_vertical"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintStart_toStartOf="@id/leftGuideline"
        app:layout_constraintEnd_toEndOf="@id/rightGuideline" />

</android.support.constraint.ConstraintLayout>
</ScrollView>

Edit: Removed RecyclerView as it wasn't necessary. As requested, button_main style:

    <style name="button_main" parent="@style/button">
        <item name="android:textColor">@color/button_main_stateful_text</item>
        <item name="android:background">@drawable/primary_action_button</item>
        <item name="android:textSize">@dimen/h5_size</item>
        <item name="android:textAllCaps">false</item>
    </style>

button_main_stateful_text & primary_action_button are just two selectors that switch between colours.