This was initially filed as an authoring tool bug, DTL-1014. When you resize the authoring tool (not predictably, and I had to keep dragging the resize handle around for a while until I reproduced it) you sometimes end up with a wrong layout. Well, it first looked like a wrong layout, but I've gotten it into a state where it's clearly an issue with repaint. Take a look at some of the screenshots in DTL-1024 (I'll attach the most relevant one to this issue as well); you can see that in one case what is supposed to be a rectangle with two lines of text here has a part of it shifted vertically as in an earthquake...

(Note, this is with the Swing stack)