Lines appear outside range of drawing window

Just got my Digi Pro 640. It works fine most of the time, but sometimes I try to draw and lines appear way outside of my drawing window instead of where my cursor is. I thought it wasn’t drawing at all but eventually discovered all the scribbles on the extremities of the page.

Any ideas?

EDIT

More details:

This happens in both Camera and Drawing views, though it seems to be much worse in the drawing view. The tablet’s scope is set on “full area”, though I’ve tried it with a few other settings with the same results.

Please help me out if you can!

Are you using two monitors?
This tablet has known issues when dual monitors are used.

Also, it may behave oddly when the pen battery power is low.
Try the pen with fresh batteries and see if you get the same results.