I'm sorry but the fix above doesn't work and I have tried a lot of other ways with no results. The bug always happens.
I spent hours to debug this issue (and many other people got it) and here my results:
1) the problem is only on Android 4.1.x and 4.2 using the default browser (on tablets and smartphones). Chrome works well.
2) When I rotate the Android device it seems the stage is not cleared so I have duplicated stuff.
It happens when I change the canvas size (i.e. canvas.width = XXX).
3) I have also tried to manually clear the stage after the orientantion change using stage.clear() or the standard canvas sintax (clearRect(x,y,w,h). Nothing!
The only workaround I really found to avoid this strange behaviors was forcing to refresh the whole page when the device is rotated (on Android devices, OS >= 3, default browser).
It's not a real solution but at least users won't see weird stuff on their screen.