When the width of a QQuickPaintedItem in a Flickable is changed then after it reaches a certain point then the whole item is rendered black

When the width of a QQuickPaintedItem in a Flickable is changed then after it reaches a certain point then the whole item is rendered black. However, if the item is initially set to that width then it is rendered fine.

In the attached example, maximize the window and then move the slider to the side then flick horizontally in the main part of the window and it will suddendly go black.