The M600 mouse tracks finger movement to perform functions such as scrolling. To prevent unintended actions, the mouse waits for up to 5mm of finger travel before it performs a gesture. This is the normal behavior of the mouse.
When scrolling, if you move your finger to the left or the right significantly enough, the mouse may issue a back or forward command to your browser. To resolve this, make sure you move your finger straight up and down (as shown in green below) when scrolling.