The AV Pro 2 serves as both a storage solution as well as a USB HUB solution for multiple connected USB devices. Therefore, it is important to ensure that all USB devices such as the Apple SuperDrive, USB flash drive, CalDigit Tuff, connected to the AV Pro 2—as well as the AV Pro 2 itself—are properly ejected from the system before powering off from the front power button or remove the power cord. This will help to avoid possible data corruption as a result of improperly ejecting your storage devices.

Additional Information:
My AV Pro 2’s LED light is off but my Drive Is still mounted?
A Note Regarding AVPro 2 Charging Capability.