There may be several reasons to why the screen on Saphe Drive freezes. Basically, what happens is that the traffic alarm has become unable to refresh the screen and therefore the same image is constantly shown. It can also happen during a firmware update of the traffic alarm that the screen shows a large downward arrow and a box under the arrow. If this image is constant, it's because the installation of the firmware has not been completed - in which case you can find a solution here: Firmware update fails


A few other things to try to refresh the screen could be: