Exchange 2013 Cumulative Update 5 Install Issue

I have tried installing Exchange 2013 Cumulative Update 5 on our server but it is failing at the Mailbox role: Transport Service section with the following error. I am running the command prompt as Administrator. Any help would be great. 

Error: The following error was generated when "$error.Clear(); Set-LocalPermissions 

" was run: "System.UnauthorizedAccessException: Attempted to perform an unauthorized operation. at Microsoft.Exchange.Configuration.Tasks.Task.ThrowError(Exception exception, ErrorCategory errorCategory, Object target, String helpUrl) at Microsoft.Exchange.Configuration.Tasks.Task.WriteError(Exception exception, ErrorCategory category, Object target) at Microsoft.Exchange.Management.Deployment.SetLocalPermissions.InternalProcessRecord() at Microsoft.Exchange.Configuration.Tasks.Task.b__b() at Microsoft.Exchange.Configuration.Tasks.Task.InvokeRetryableFunc(String funcName, Action func, Boolean terminatePipelineIfFailed)".