Position a textbox in Microsoft Word with VBA

With the following code, I create a textbox around some text and try to anchor it in the correct spot:

With Selection
    .CreateTextbox
'    Selection.ShapeRange(1).Width = InchesToPoints(7.3)
    With .ShapeRange(1)
        .Width = InchesToPoints(7.3)
        .TextFrame.AutoSize = True
        .RelativeVerticalPosition = wdRelativeVerticalPositionLine
        .Anchor.Application.ActiveDocument.Bookmarks("textboxAnchor").Range.Select
    End With
End With

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The bookmark "textboxAnchor" is located just before "Chief complaint" in the correct place image below. I tried putting the anchor in different places with no luck.

It all works well except the location of the textbox sometimes moves. Here is where I want the textbox:

Here is where the textbox often ends up (above "Date of visit" instead of below it):

Any idea how I can properly locate the textbox on the page using VBA?  TIA