8 TB Disk dying - or is it the Controller?

During the last copy operation of my Seagate 8 TB disk (connected via USB 3.0), the speed of my disk dropped dramatically (from 90 MB/s to 100 kB/s). So I took CrystalDiskInfo to check the SMART values and a lot of the raw values increased drastically:

_{Highlighting by me for the values that gre rapidly}

Now someone told me that this might happen when the is connected via USB. The info was that it could be a controller issue instead of a disk failure.

Is that possible? What test could I run in order to figure that out?

It would seem highly, highly likely its a disk issue rather then a controller one. SMART values are a report of what a hard disk thinks of itself so it does not matter if its queried over USB or otherwise - the disk thinks its the problem.

As the disk is likely on its way out, getting a second disk and finding a computer where you can plug both disk in on the SATA interface and doing ddrescue from the old to the new disk will copy the data off and show you the speed and what parts of the disk are dying. (really you could just do a read from the disk when connected to SATA, but that is going to increase the data loss/risk)