My QNAP TS-453 Drive number 3 is sluggish (Low Throuput)?

I had a problem accessing some of my larger directories. It used to be OK, but started slowing down. Ran a few tests and found that drive Number Three's throughput was very low. Western DIgital sent me a replacement. I used the "Replace Disks one by One" command to change out this drive. At the end we will retest the new drive throughput.

The video is indexed so you can chose what you want to see.

All of my videos are "one take only". If I make a mistake, I try to correct another way, either "on the fly" during the video or with text...