(I will post screenshots of these errors after I reboot back into Windows).
The first one, "ia Stor AV" is the one that makes the UI freeze for a bit, and then if you do more intensive disk IO, the second error starts appearing, and literally thousands and thousands of those come in the log, and after that starts happening you can't access the array any more before a reboot. Well my driver isn't after 14.x, as seen on the screenshot below - I wonder if there really isn't a better driver?
I couldn't find any other Intel drivers and when I searched for the RST drivers on Intel's own site, I could only find ones for Windows XP upto Windows 8.1, but none for Windows 10.
For now I'm left with a PC that I can't use, because I can't go back to Windows 7 and Windows 10 is not working with my RAID arrays.
So, I figure that I might have just got unlucky and the old WDC drive actually developed read errors, although it's strange that it happens exactly when I install Windows 10 (these drives are something like 7 years old).
Well I can't copy the contents off the disk from Windows since it keeps failing as described above, so I boot into Ubuntu Linux from a USB stick, so I can use ntfsclone to image the J-drive to another disk.