Delegation difference between ARSShell and MMC?

Hello everyone,

I'm trying to set temporal group membership via powershell for protected groups (Admincount 1) but always the following error message:

Exception: Administrative Policy returned an error.
Attempted to perform an unauthorized operation.

If I try to do the same using the MMC with the exact same user, I can add the user without any issues.

Parts of the script:

$ProtectedGroups = Get-QADGroup -LDAPFilter "(admincount=1)" -Credential $cred -Service $TargetARS -Proxy -SearchRoot $Searchroot | Select-Object Name,dn | ForEach-Object {$_.dn}

If ($ProtectedGroups -contains $TargetGroup)
   $null = Add-QADGroupMember        -Identity $TargetGroup -Member $Member -Credential $cred -Service $AdminARS -Proxy -Control @{'ScheduledOperation-SetTime'=$StartDateTime}       
   $null = Remove-QADGroupMember -Identity $TargetGroup -Member $Member -Credential $cred -Service $AdminARS -Proxy -Control @{'ScheduledOperation-SetTime'=$EndDateTime}

The account has delegated rights to add/remove group members.

Is there a differnce on how ARS shell handles delegation?