QTreeView branch indicator changing icon randomly?

Hi,

Since changing from Qt4 to Qt5 I am having a strange problem where the expansion indicator for my QTreeviews are changing from one icon to another after selecting an object within the tree and I cant figure out where this is happening.

I am not setting any stylesheets on any of the QtreeViews within my project and have also set a breakpoint on QWidget::setStyleSheet which is never hit. Does anyone know of any other way this icon can be set.

The icon starts out as is below

Attachment 12059

then changes to the plus/minus symbols after selecting a child in the tree.

Attachment 12060

It also seems like there is no icon set for the hover over as the icon just becomes a white square.

Any thoughts would be appreciated.

Thanks

Jonny