Never had voltage too low issues. I've had it tell me voltage was too high when I try to flash in the summer heat right after shutting the car off.
I also had one that the USB connection snapped off the Tactrix PCB. My second is pretty abused in the USB port area too.
Now I use one of these USB cables to keep my knobby knees from whacking the USB cable:
The straight cords just stick out too far.