LINQ Giving Invoke code: Exception has been thrown by the target of an invocation. Exception

Hi, I am attempting to Add a DataRow to an empty DataTable. Using LINQ.
This is my LINQ query:

Dim q = (From d In Source.AsEnumerable()
	          Let fileName = d.Field(Of String)("a.input_extern_file_name")
	          Let ra_sys     = d.Field(Of String)("a.ra_sys")
	          Let colName = d.Field(Of String)("ColumnName")
	          Let remarks  = Reference.AsEnumerable().Where(Function(f) f.Field(Of String)("INPUT_FILENAME") = fileName).Count()
	          Select d)
For Each missingFile In q

For every row in the Source datatable I am taking the value from the “a.input_extern_file_name” column and Counting the number of times it occurs in the Reference datatable’s “INPUT_FILENAME” column and then the number if times it occurs is stored in the “Remarks” column of the Source datatable. And then I am trying to add the Row to the Missing datatable.
However I am getting this error:

RemoteException wrapping System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.  ---> RemoteException wrapping System.ArgumentException: This row already belongs to another table. 
   at System.Data.DataTable.InsertRow(DataRow row, Int64 proposedID, Int32 pos, Boolean fireEvent)
   at UiPathCodeRunner_6fd11f9842d1403f9fc17b67fcc16d7a.Run(DataTable Reference, DataTable Source, DataTable& Missing)
	--- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor)
   at System.Reflection.RuntimeMethodInfo.UnsafeInvokeInternal(Object obj, Object[] parameters, Object[] arguments)
   at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.RuntimeType.InvokeMember(String name, BindingFlags bindingFlags, Binder binder, Object target, Object[] providedArgs, ParameterModifier[] modifiers, CultureInfo culture, String[] namedParams)
   at UiPath.Activities.System.Utilities.InvokeCode.CompilerRunner.Run(Object[] args)
   at UiPath.Activities.System.Utilities.InvokeCode.NetCodeInvoker.Run(String userCode, List`1 inArgs, IEnumerable`1 imps, Object[] args)
   at UiPath.Core.Activities.InvokeCode.Execute(CodeActivityContext context)
   at System.Activities.CodeActivity.InternalExecute(ActivityInstance instance, ActivityExecutor executor, BookmarkManager bookmarkManager)
   at System.Activities.ActivityInstance.Execute(ActivityExecutor executor, BookmarkManager bookmarkManager)
   at System.Activities.Runtime.ActivityExecutor.ExecuteActivityWorkItem.ExecuteBody(ActivityExecutor executor, BookmarkManager bookmarkManager, Location resultLocation)

Attached is my Workflow. Kindly assist. Thank you in advance.
Filter.xaml (12.4 KB)

Kindly note: we can reduce the black box as we can make it work within an assign activity
when adding the row to another table then we have to respect the holding origin table and would do it with the item array

For Each missingFile In q

referring to the description and the LINQ we would also get in doubt and feel that there are some missmatches. However get it firstly run and check the result

Also it is a cross reference:

Why are you going through all this when you could simply use the Add Data Row activity? You’re reinventing the wheel…