Narrowed Seekbar button on sliding in Android (with own thumb xml)

I've got problem with Android SeekBar.

When I use standard thumb (blue) it's OK, but when I use own theme like scrubber_control.xml there is problem - button is narrowed. I've tried setting minimal height, padding, adding height / width to scrubber_control item, but can't fix that strange issue.

layout

<SeekBar
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:id="@+id/question_seekbar"
android:thumb="@drawable/scrubber_control"
android:maxHeight="3dp"
android:minHeight="3dp"
android:paddingLeft="15dp"
android:paddingRight="15dp"
/>

scrubber_control.xml

<selector xmlns:android="http://ift.tt/nIICcg">
<item android:state_enabled="false" android:drawable="@drawable/scrubber_control_disabled_holo" />
<item android:state_pressed="true" android:drawable="@drawable/scrubber_control_pressed_holo" />
<item android:state_selected="true" android:drawable="@drawable/scrubber_control_focused_holo" />
<item android:drawable="@drawable/scrubber_control_normal_holo" />
</selector>