QGraphicsScene rendering artefacts when overlaped window (QlineEdit) has blinking cursor

My GraphicsScene has many moving items, and scene painting on the view takes some time.
My QGraphicsView overlaped with QlineEdit (QlineEdit has parent QGraphicsView). When QlineEdit has focus his cursor is blinking.
When text cursor in QlineEdit showed/hided then moving items (and/or background) around QLineEdit rendered with artefacts.

In attached example I increase speed of cursor blinking for visualising artefacts. (with QApplication::setCursorFlashTime())
For viewing this bug:
1. LineEdit must be in focus
2. Size of toplevel window should be such that the circle moved around LineEdit.