[LP 2G/32GB Not activated] - Arduino problem - "USB" err. 43

Hi Guys!
I've a problem with this board: sometimes the USB2 ports don't work properly.
In the "Device Manager", the "Generic HUB USB" failed to start with the error "The USB hub failed to reset. Err43"(see attachment).
In this situation the Arduino COM port disappears from the Device Manager. Reboot of the Arduino doesn't solve the problem.
Sometimes the TX Led turns on without any sketch uploaded!
I've used FIT0501 as power adapter and only DFR0330 connected to USB2.
These items works properly on the others boards.
If I reboot the board without any devices connected, the USB2 ports work properly.
Sometimes LP doesn't boot: stuck at Shell> command. I've to reboot the board two or three times before that the OS boots properly.
What do you advise me to do? It could be a defective board?

Thanks a lot!
Pasquale