Very often, the device just shuts down during operation.
Typically, I use it on the bicycle, and the screen is switched off after a few seconds. For viewing my current position, I press one of the buttons. Sometimes, I must see that the device the starts. And the map proves that it crashed some time before that. Some of those crashes were reproducible with some 50% - e.g. near a round about in Alcudia.
But sometimes the device just crashes when saving/editing waypoints.
Firmware 3.90 is installed; the problem was not so severe with older firmware.
What are your experiences?