If you hit the pulldown switch of the rubber size, you need to be quit left of the downarrow-sign.
If you are more than the middle on the right, the pulldown size select closes immediately.
If you reach the borders at the right and at the bottom of a picture by using the rubber, the rubbercircle
disappears behind the border of the picture and become an arrow, but if you try to touch the scrollarea,
the rubbercircle appears again.
Best Regards