In the GPS set up menu, there is a item that I believe is called DGPS that you can switch on or off. It is a degraded signal that can get you close to your target, but leaves a margin of error. Because of this, the unit can show you as moving when you really are not.

Another item to consider is how fast you have your track log leaving a tracking marker. You can adjust the time between points ( markers ) to, #1 ) to save memory space by marking fewer points, and

#2 ) fewer points marked shows less detail, fewer curves and twists in the track log screen display.

If you have your owners manuel, take a look init and try to find out about these items.

And next time buy a Garmin GPS. IMHO they are the best unit made - period. I am on my 2 nd one. The first was stolen. I have been using them since about 1993. I have tried Magellan and Lowrance also.Garmin is the only unit I will ever buy.