What likely happened is you moved the mouse and when it stopped there must not have been a change in the screen, so DemoWorks did not generate a new frame here. You can avoid this while recording if you click the mouse (but sometimes this is not possible if clicking will do something you don't want).
The way the mouse animation works is each frame has 1 mouse movement which starts at the beginning of the frame and stops at the end of the frame. If that frame was 20 seconds then the mouse will take 20 seconds to do that frame's mouse movement. If the mouse is not moving then this is accomplished by having the frame's start and end mouse position equal to the same spot. You can't have 1 frame that includes some movement and some non-movement.
Basically, your demo is likely missing a frame where the mouse does not move. If this is the case, what you can do is decrease the time of the "mouse creep frame" so that the mouse moves faster and then add a new frame after it by copy/pasting an existing frame where the mouse will not move. I hope this makes sense.
Regards,
Greg