I am currently using a Samsung M3 1TB USB portable Hard Drive to archive recordings from the 4000T. On most occasions the 4000T boots up normally, recognises the USB drive and lists the recordings on the internal and external drives. On several occasions however although the external drive is recognised (USB splash message on boot)the recordings are no longer listed and can’t be accessed. More seriously, when this occurs, on putting the unit back into standby the hard drive will not spin down and stays permanently active. The external USB drive also remains active with activity LED blinking 4 times every 10 seconds or so. The only way to get the 4000T into full standby mode is to switch off the power and switch back on. Not sure whether this is a bug or whether certain USB drives can cause this erratic behaviour.