Getting System.NullReferenceException while copying the columns from one workbook to other wokbook

Getting System.NullReferenceException while copying the columns from one workbook to other wokbook. This is an intermittent issue, we are using the following piece of code for copying the columns.

upgradingWorkbook.Worksheets[workSheet.Name].Cells.CopyColumns(workSheet.Cells, 0, 0, workSheet.Cells.MaxColumn + 1, new PasteOptions() { PasteType = PasteType.Formats });

please see the below stack trace

{“assembly”:“Aspose.Cells, Version=19.8.0.0, Culture=neutral, PublicKeyToken=716fcc553a201e56”,“method”:"\b .\b \u0005",“level”:0,“line”:0}
{“assembly”:“Aspose.Cells, Version=19.8.0.0, Culture=neutral, PublicKeyToken=716fcc553a201e56”,“method”:“Aspose.Cells.Cells.ClearContents”,“level”:1,“line”:0}
{“assembly”:“Aspose.Cells, Version=19.8.0.0, Culture=neutral, PublicKeyToken=716fcc553a201e56”,“method”:“Aspose.Cells.Range.\u0002”,“level”:2,“line”:0}
{“assembly”:“Aspose.Cells, Version=19.8.0.0, Culture=neutral, PublicKeyToken=716fcc553a201e56”,“method”:“Aspose.Cells.Range.Copy”,“level”:3,“line”:0}

@taruney,
Could you please share complete sample code (runnable) and your template file. We will reproduce the problem and provide our feedback after analysis.