I assume this is the source. The drive has the label "TerrorData" and then you have a folder on that drive called "TerrorData". Is that correct?
Are there any data in that folder?
Yes, that's right, I named the drive and the folder the same thing. Might that be causing all the problem? There's loads of data on TerrorData, I plugged it in directly into my Elementary machine the other day to use Gparted to remove the space from the name of the disk and I checked that the data was OK - browsed through the folders, played a couple of files. As you can see from the screen grab 1.64TB has been used