constant read-access to my external HDD - is it Windows 10?

I have a 4Tbyte external hard drive (USB3) and when it is connected, it constantly flashes as there is "something" that will read at all times. How do I find out what program/service is doing this?It is NOT virus killer, defragmentation or debugging (the one in Windows).
As seen in the picture, (DISK 4), it does it even if I remove the drive letter (used to be H:), so it is not something to do with logical driveletters, I think.Only process that has constant access to HD in the job list is the systemfile called (ntoskrnl.exe) and it is quite low, but it is there. According to performance measurement, is read with 15-17 kb / s, so it's very slow, whatever it is. When I read / write to the disk myself, it runs at full speed, so it's not the disc itself that is blunt.I have left it turned on to see if it stops, but now it has been lit for 26 hours and there is constant access to it. What can it be?

It started after one of the windows updates, and now my extern HDD will not go in sleep-mode anymore because of this. How do I stop this?

Why is this thread moved to "Drivers and hardware"? I don't think this is a driver problem, as it has started after a windows 10 update. And there has not been new drivers for USB3 in a very long time.