Application-defined error or object defined error while copying chart using VBA

Hi , 

Can you please help me figure out the problem I am facing with Word , VBA , Excel ? 

I am trying to copy a chart present in an Excel workbook into a Word document using VBA  macro , created in the Word doc ( Macro code is given below ) . 

The problem is that the macro gives following error : 

Run-time error 1004 :

Application defined or object defined error 

Now , if I simply open the excel workbook  , randomly click on some cells and save  it  (  note that no changes are done to the chart in question )  and re-run the  macro , then the problem goes away . 

I am unable to solve this problem . 

Macro code : ( Problem line is in bold ) 

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Sub copy_chart()
'
' copy_chart Macro
'
'

Set oExcel = CreateObject("Excel.Application")
oExcel.Visible = True

Set wb = oExcel.Workbooks.Open(Application.ActiveDocument.Path & "\" & "Chart_copy_problem_1.xlsx", UpdateLinks:=False)

wb.WorkSheets("Regression results").ChartObjects("Cov_chart").Chart.ChartArea.Copy

ActiveDocument.Bookmarks("Chart_here").Select
Selection.Paste

oExcel.Workbooks("Chart_copy_problem_1.xlsx").Close

oExcel.Application.Quit

End Sub

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