To reproduce this:

1. Run any example program, e.g., HelloWebView

2. Resize the window repeatedly from the lower-right corner

3. BUG: you will see flickering where the stage is sometimes painted with just the background color

This is a recent regression. It is most noticeable with a complicated scene, such as HelloWebView or Ensemble8, but I can also see flickering with HelloRectangle or HelloAnimation.