Qt Quick Designer - render to image update issue with Qt Quick 2.0

How to reproduce?

Not 100% deterministic
Drag in a couple of Rectangles
Typically after dragging in 4-5 Rectangles no Items are updated
any more in the form editor.

More precisely: While size and position are still changing Items are not
re-rendered (e.g." the text of Text Items does not change and the color of Retcangle).

We render the items using DesignerSupport::renderImageForItem()
(qtdeclarative\src\quick\designer) which again uses:
QQuickShaderEffectTexture::toImage().

Updates are still issued but QQuickShaderEffectTexture::toImage() always returns the old outdated image (old color/text).