I use Kahn Academy for private tutoring, so I use the exercises as examples and checks for teaching the concepts.  I am constantly having problems when drawing on exercises with a Wacom model CTL-4100:

1.  Every time I make a small line or a point (like a decimal), immediately a menu comes up that is equivalent to a left button mouse click.  I click on the screen in order to make the menu disappear, but if I do this quickly, I often accidently click on something on the menu and this disrupts the whole process and I lose the screen that I'm working on.  Note:  I am not pressing the button on the stylus.  The menu comes up every time I draw something small.

2. If I switch out of the exercise screen and then come back to it, I can no longer draw using my tablet and stylus.  I have to refresh the page to start drawing again, but then I lose everything I've drawn up to that point.