zooming while drawing a freehand mask, results in invisible mask

Since I know PHOTO-PAINT (since version X4), it is a problem to zoom (mouse wheel) during drawing a freehand mask. A few month ago I bought CGSX7, and thought that this problem should be fixed - unfortunately not.

Detailed Problem:

The drawn freehand mask get invisible if I zoom with the mouse wheel while the mask isn't finished/closed. If I make another click to draw the next line of the freehand mask, the shown frame of the mask isn't the frame i really drew - the now shown mask is a combination of the last set point, the start point and next-point.

Is this a volitional behavior of PHOTO-PAINT? If so, please can someone explain me what's the idea behind this "malfunction"? Is there a bugfix or workaround?

best regards