[Scanner much slower on one drive]

No, all 4 disks show the same temperature - around 32°. In fact, all Stablebit's data is pretty well identical for all 4 drives.

[Scanner much slower on one drive]

I have just bought 4 4TB Western Digital Red Plus drives, and am in the process of having Scanner scan them for the 1st time. All have the same firmware version.

3 of them scan at about 1% every 25 seconds (increasing by about 0.13% each time), while the 4th scans at 1% about every 113 seconds (increasing by about 0.02% each time). What might account for this variation?