The following test case will fire the onmousetrackup event twice when you drag the red view onto the green view. The even should only be fired once. This worked correctly in 4.0.2.

<canvas height="100%" width="100%" proxied="false">
<view width="40" height="40" bgcolor="red">
<method event="onmousedown">
LzTrack.activate('item');
this.bringToFront();
dragging.apply();
</method>

<method event="onmouseup">
dragging.remove();
LzTrack.deactivate('item');
</method>

<dragstate name="dragging"/>
</view>

<view x="200" y="200" width="100" height="100" bgcolor="green">
<method event="oninit">
LzTrack.register(this, 'item');
</method>

<method event="onmousetrackup">
Debug.write("mousetrackup");
</method>
</view>
</canvas>