Windows Server Essentials 2012 error code: 2147942403 The system cannot find the path specified

Running Windows Server 2012 Essentials with an external usb 3 drive as a backup device.  Using a Vantec hx enclosure with a WD Red drive. Last night the Dashboard saw the drive with about half the 4TB available for backup. A.M., I get "error code: 2147942403 The system cannot find the path specified".

Going to the server desktop, I see a message indicating that the usb device malfunctioned.  unplugging it, and plugging it back in, I now have it available via the dashboard.

This has happened a couple times with two different drives in Vantec hx enclosures.

A couple possibilities come to mind:

1. the enclosures may both be bad...
2. there is some problem with the system software and external usb drive.

Thoughts?

Suggestions for external enclosures?

Thanks!