MauriceModV

To put this right, ESET doesn't deactivate Defender. It's Windows itself that deactivates / reactivates Defender when a 3rd party AV registers / unregisters from the Windows Security Center.

Sorry for the late reply, had to verify on more than 1 PC.

At first, yes it was the active Defender! (in conjunction with the security update and Eset)
Typically ESET deactivates the Defender on installation and everything is fine, I don't know why and I can't tell atm for sure which case is correct:
- Defender was still running on these few PCs, never had a Problem until the Security Update changed something
- Defender was not runnung but the Security Update activates it for whatever reason, bug, ...

I'm not done fixing all PCs, maybe there is one PC left to find out which case is correct.

Thanks to all!

Hi,
a similar problem with copying folders and files appeared in our company.
The solution turned out to be that Windows Defender was enabled even though ESET was installed. Disabling Windows Defender in the registry solved the mentioned problem.

Everything is on 64bit, I double checked it.