🚀 go-pugleaf

It looks as if you just deleted your myTopTextFrame.ParentStory in line 4? So can you reference it in myTopTextFrame.ParentStory.InsertionPoints.Item(-1).Contents = iPre?

This is how I've been emptying out a string of text frames then placing some text in it. The text frames are linked starting with a 1 column headline box then 2 column body boxes. Might it help you?
Sub test_place_copy()
Dim myInDesign As InDesign.Application
Set myInDesign = CreateObject("InDesign.Application")
Set myDocument = myInDesign.ActiveDocument
' remove any excess body text
Do
myDocument.TextFrames.Item("Document_Body_1").Contents = ""
Loop Until myDocument.TextFrames.Item("Document_Body_1").Contents = ""
Do
' remove any excess headline text
myDocument.TextFrames.Item("Document_Body_Headline").Contents = ""
Loop Until myDocument.TextFrames.Item("Document_Body_Headline").Contents = ""
' place the text from this path
text_path = "C:\text.rtf"
' place the text
myDocument.TextFrames.Item("Document_Body_Headline").Place (text_path)
End Sub