How-to correct a non-scrolling GPS unit
When following a stored track, your GPS should keep your current position in the middle of the screen and make the stored track scroll past it. Sometimes this goes wrong and you will find that your current position begins to move off-centre and will eventually go off-screen.
In addition to your current position moving off-centre you will notice that you now have an arrow-head symbol on the screen. (Its colour varies with model of eTrex)
Something has jogged the thumbstick off-centre and it has entered a mode used to report the Grid Reference of any point to which you steer the arrow-head.
Easy! Just press the "Back" button once and you should now see your current positon in the cetre of the screen and the arrow-head will have vanished.