MIM Powershell MA Error Report

[DrBlackBird]

I migrate my Powershell Management Agent from an older Version and get an error in the "End Import" script part.
The script run successfully in Version:
FIM Powershell Management Agent Version 4.3.1082.0
Now I tried these versions:
MIM Powershell Management Agent Version 1.1.830.0 and Version 1.1.8610
The script is quit simple
[CmdletBinding()]
param(
[Microsoft.MetadirectoryServices.ConfigParameterKeyedCollection]
$ConfigParameters,

#[ValidateNotNull()]            
[Microsoft.MetadirectoryServices.OpenImportConnectionRunStep] $OpenImportConnectionRunStep,  
#[ValidateNotNull()]            
[Microsoft.MetadirectoryServices.CloseImportConnectionRunStep] $CloseImportConnectionRunStep,          
            
[PSCredential] $PSCredential,            
        
[string] 
$scriptDir = [Microsoft.MetadirectoryServices.MAUtils]::MAFolder             

)
$result = (New-Object Microsoft.MetadirectoryServices.CloseImportConnectionResults)
$result.CustomData = "My custom data"
Write-Output $result

The Error is:
The extensible extension returned an unsupported error.
The stack trace is:
"Microsoft.MetadirectoryServices.ExtensionException: The following exception occurred while executing the PowerShell commands: System.NullReferenceException: Object reference not set to an instance of an object.
at Microsoft.IdentityManagement.Connector.PowerShell.Engine.PowerShellRuntime.InvokePowerShell(PSCommand command)
at Microsoft.IdentityManagement.Connector.PowerShell.Engine.PowerShellRuntime.InvokePowerShell(PSCommand command)
at Microsoft.IdentityManagement.Connector.PowerShell.Engine.PowerShellContext.ExecuteScript(List`1 commandParameters, String scriptFilePath, Boolean enableSetLocation)
at Microsoft.IdentityManagement.Connector.PowerShell.Bridge.ImportBridge.GetCloseImportConnectionResult(String scriptFileConfigKey, CloseImportConnectionRunStep closeImportRunStep)
Forefront Identity Manager 4.5.202.0"

If I do not use a script in "End Import" at all, the sync runs without error. But I need this step to set additional information in the CustomData field.
Any help is appreciated

Best regards,
Thomas