[SOLVED] USB transfer speed plummeting to zero?

[NaranJust]

I have an issue with USB transfer speeds. The speed at the beginning of any transfer is zero and it stays like that for around 20 seconds.
Then it starts transferring, but the speed keeps plummeting to zero every 20ish seconds, before going back up to speed (~15 MB/s) again.

Screenshot (at the dips, the numbers say zero but the graph doesn't show 'zero'):
https://prnt.sc/rh0szf
Copying from USB to HD/SSD does the same thing (https://prnt.sc/rh1e2b), except the max speed is around 124 MB/s.
It's the same for both front and back USB slots and for different USB sticks (tried 3 or 4 of them). Formatting doesn't help.

Everything worked fine when I installed Windows (a month ago).
I haven't changed BIOS or any drivers until then, except an hour ago when I tried out some fresh chipset drivers which haven't solved the issue.
It's worth mentioning that the transfers are always successful, but the 'speeds' bother me since it's a new PC and I haven't had the issue before.

Specs: i7-9700K, Z390 Aorus Pro, Samsung Evo SSD, WD Black HD, Windows 10 Pro (updated)

P.S.
One of the last things I did (that's maybe worth mentioning) is that I installed vJoy which allows me to map keys in Forza Horizon 4
to my wheel and gamepad at the same time. It has an option 'Mute devices' but it is turned off and it should only affect my wheel and gamepad.

 

[Ralston18]

Look in Task Manager and Resource Monitor for anything related to vJoy launching or running in the background.

Disable and then test the USB transfer speeds again.

Also: how many USB devices are connected? Do they have their own power sources or are they relying on host computer USB power?

More to the point would be to uninstall vJoy and then again test USB transfer speeds. If the speeds return to previous levels then that would indeed implicate vJoy.

 

[NaranJust]

The Resource Monitor shows the same thing. Dropping to 0 at somewhat fixed intervals (30s normal speed, 30s zero, 30s normal, 30s zero...).

As for USB devices, I have a keyboard, mouse, webcam, and headphones. They are all relying on computer's USB power and these same devices didn't cause any issues on my previous PC.

vJoy was just extracted, not installed. It's not running so I guess it's not the one causing issues.

What happens if I uninstall Intel 3.1 eXtensible thingamajig? Will it reinstall itself after restarting the PC?

 

[NaranJust]

Oh my... I guess the problem was in the WD service.

I've stopped the WD Drive service (for my external HDD, which was not plugged in) and now the speeds are back to normal.
I've completely uninstalled WD Discovery and other tools, so I'll monitor my speeds these days to see if that was the culprit.