Unable to iterate the CustomerData collection (Invalid Procedure Call error) - vba

Question

I am attempting to store xml metadata within chart shapes in a PowerPoint presentation.
I need to ensure that the shape only contains the current xml data, so I have a function to delete existing data (if any) and add the current data.
Sub Test()
Dim cht as Chart
Dim xml as String
Set cht = ActivePresentation.Slides(1).Shapes(1)
xml = "<Chart property1='true' property2='false'>blah blah blah</Chart>"
EmbedChartXML xml, cht
End Sub
Sub EmbedChartXML(xml As String, cht As Shape)
Dim x As Variant
'Get rid of any previous data
For Each x In cht.CustomerData
x.Delete
Next
Set xmlPart = cht.CustomerData.Add
xmlPart.LoadXML xml
End Sub
The For Each loop is failing with the indicated error message. I can see that the cht.CustomerData.Count = 2 (for example), but if I try to view this in the Locals window, I get the same error.
UPDATE
Here is another test routine that is failing, even though there is nothing inside the For/Next loop.
Sub TestIteration()
Dim sld As Slide
Dim pres As Presentation
Dim shp As Shape
Dim x As CustomXMLPart
Set pres = ActivePresentation
Set sld = pres.Slides(2)
For Each shp In sld.Shapes
Set pptCustomerData = shp.CustomerData
For Each x In shp.CustomerData
' For Each pptCustomXMLPart In pptCustomerData
' Debug.Print pptCustomXMLPart.Id
' Next
Next
Next
End Sub

Answer 1

Others here cannot replicate this error in Excel 2013 (I am using Excel 2010) where the collection object itself becomes inaccessible. Perhaps there is a bug or something, but I could not find much on Google about similar errors...
I ultimately arrive at this solution. I am not sure why the CustomXMLPart's .Delete method doesn't actually delete the item from the collection (instead it makes it to Nothing, and then failure on successive iteration attempts).
Instead, I use the CustomerData.Delete method. This seems to be working as expected.
Sub EmbedChartXML(xml As String, cht As Shape)
Dim x As Variant
Dim cData As CustomerData
Dim xID As String
Set cData = cht.CustomerData
Debug.Print cht.CustomerData.Count
'Get rid of any previous data
For Each x In cData
xID = x.Id
cData.Delete xID
Next
With cData.Add
.LoadXML xml
End With
Debug.Print cht.CustomerData.Count
End Sub