wrong checksum in VirtualBox due to Windows Defender Credential Guard?

I use Virtualbox a lot on my Laptops for all kind of playgrounds. I install the software to test in the VMs and do whatever is required for my test. 
But in one VM, I could not install a specific package. 

It seemed to me the checksum of the package to install was always wrong. 

I tried several ways to get the package onto the VM, like downloading it directly with wget, using an alternate repository, download it to my Windows laptop first (there the checksum was correct) and transfer it to the VM, ... 
Every time the checksum was wrong - but different! 
It differed depending on the position in the VMs filesystem. 

After some research this led me to a question on stackexchange. 
And some more clicks later I hit the DG_Readiness_Tool. 

It really seems, Microsofts Defender somehow affected either the reading of the file in the VM or the calculation of it's checksum. 

However, after going through the articles noted above (and some more) I decided to give it a try with 

DG_Readiness_Tool.ps1 -Disable -AutoReboot

The Laptop rebooted - and everything is fine now. 
(I had to re-load the package into the VM - this gives some clue where the issue happened, But I have no prove so no finger-pointing here)

I can not explain, why (and how) this happened, and I don't recommend to disable ANY security-feature. Just in my case it helped. 

(On another, quite similar, system the same VM with same package and also up-to-date Win10 never showed such issues)