Mouse lock on a widget in the RetainerBox is misaligned and locked in the wrong position in the standalone/package application

Locking the mouse to a widget covered by a Retainerbox locks it in a different position in the standalone/packaging application than in PIE.  This does not happen if RetainerBox is disabled and the mouse is locked in the correct position. Also, selecting focus outside the viewport locks the mouse in the correct position. 

1. Open the attached repro project
2. Play in editor
3. Move mouse cursor on the bottom position in scroll box, then move scroll and mouse lock 
4. Stop PIE
5. Play in standalone 
6. When the mouse cursor is moved to the bottom of the scroll box, the mouse lock is locked at a position well off the scroll box