window position/size restored unintentionally when aero-snapped haroopad get focused

How to reproduce symptom:

In Windows 8.1, Get Focused in Haroopad, then press Win+LeftArrow, then press Alt+Tab to switch to another window, then press Alt+Tab again to return back to the Haroopad. 

Then the Haroopad window position/size will get restored to the state just before do aero-snap.