Mine has failed to power up a few times recently. I think I've identified two causes. The first is when I don't unplug the adapter from the lighter socket, turn the car off, exit the vehicle and hit the auto lock/alarm on button on my key fob, which maybe interferes with proper shutdown of the WF1 or somehow sends a surge to the unit because it is still connected to the socket. When I've come back to the car after doing that, the unit doesn't power up, and holding the button down for more than 10 seconds doesn't reset it. It is bricked. But waiting 12 hours has solved the problem and it works again the next morning.
I've also had a situation where I've pulled the adapter very quickly after the "system shutting down" announcement, and that also temporarily bricked the camera. But it started up again the next day.
Things to keep an eye on.
There is also a horrendous amount of static electricity here in the winter - very cold and extremely dry, so that may also be causing intermittent issues.