Hi dyson.
There appear to be some nil objects within the mastergroup which are causing the copying of display objects in setParentGroup to fail. I did a quick work around by just simply adding mastergroup as a child of the parent group. I guess another fix could be to check if a given child is nil before attempting to swap its parent.
(could this be due to the recent noDraw updates?
are some objects being nulled before being removed from the mastergroup?