Thanks for your posting and considering Aspose.Cells.
I am unable to find out the problem you mentioned. Please see the code below and the output xlsx file.
Both string and numeric data appears
When I opened in Open Office 3.3, it shows fine. Please see the screenshot.
Please download and use the latest version:
Aspose.Cells for .NET (Latest Version)
If the problem still persists, then please create a sample application to replicate the problem and post it here, we will look into it and help you asap.
string filePath = @“F:\Shak-Data-RW\Downloads\source.xlsx”;
Workbook workbook = new Workbook(filePath);
workbook.Save(filePath + “.out.xlsx”);