Symptoms
If you run the Get-Help cmdlet for an instance of Microsoft Exchange Server 2016 that is deployed on Windows Server 2016, you receive an error message that resembles the following:
[PS] C:\>Get-Help Get-MailboxDatabase
Get-Help : Exception calling "Open" with "0" argument(s): "The following error occurred while loading the extended type data file: Error in TypeData "Deserialized.System.Management.Automation.DebuggerCommandResults": The member TargetTypeForDeserialization is already present. Error in TypeData "System.Management.Automation.DebuggerCommandResults": The member SerializationDepth is already present. [….] "Microsoft.Exchange.Data.Directory.Management.RunspaceServerSettingsPresentationObject": The member SerializationData is already present. Error in TypeData "Deserialized.Microsoft.Exchange.Data.Directory.Management.RunspaceServerSettingsPresentationObject": The member TargetTypeForDeserialization is already present. " At line:1 char:1 + Get-Help Get-MailboxDatabase + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [Get-Help], MethodInvocationException + FullyQualifiedErrorId : RuntimeException
Resolution
To fix this problem, install the Windows Server 2016 March 2018 cumulative update.
