CAU - One or more unexpected accounts with write permissions were encountered wen checking the security

Hi,

We have 4 seperate WS2012R2 Hyper-v clusters located in 2 datacenters.
I want to setup Cluster aware updating - remotely managed.
The plan is to orchestrate the update process from a third location.  Also on this third location the fileshare with the hotfixes will be located.
I will download the Hyper-V hotfixes and Failovercluster hotfixes and place them in the following folder structure:

\\MyFileServer\Hotfixes\Root\
   DefaultHotfixConfig.xml
   CAUHotfix_All\
      Update1.msu
      Update2.msi
      Update3.msp
      ...

I will only use the MicrosoftHotfixPlugin.
I have made a share and set the ntfs permissions as
SYSTEM                Full Control
Local Administrators        Full Control
CREATOR Owner            Full Control
TrustedInstaller        Full Control
Users (local)            Read&Execute

When I check the ACLs via Get-Acl -Path C:\Hotfixes\Root | fl AccessToString I get
...
BUITLIN\Users        Allow    ReadAndExecute,Sychronize
BUITLIN\Users        Allow    AppendData
BUITLIN\Users        Allow    CreateFiles
...

I set the encryption: Set-SmbShare -Name Hotfixes -EncryptData $True -Force
If I start the Preview Updates with paramteres I get the error: "One or more unexpected accounts with write permissions
were encountered wen checking the security for :\\MyFileServer\Hotfixes\Root\ Unexpected accounts:
{BUILTIN\Users, Sid:S1-...}.

Why is this happening? I haven't changed the permissions for the local users group?
Anybody else has implemented CAU with remotely managed using an SMB fileshare?