NPOI corrupting xlsm workbook

Question

I am required to write some data into an macro enabled workbook which was developed in 1998, i am using NPOI dotnet core library for this task. I am able to write the values into the excel correctly, however i am seeing that alignment and formatting of the sheets is lost. Screenshots below:

First one shows the file after open the file using NPOI and downloading the same, and second shows the file when it is locally opened.

below is the code i am using

public XSSFWorkbook OpenExcelFile(string filePath, string tempSavePath)
        {
            using (var stream = new FileStream(tempSavePath, FileMode.OpenOrCreate, FileAccess.ReadWrite))
            {
                var temphssfwb = new XSSFWorkbook(OPCPackage.Open(filePath));
                temphssfwb.Write(stream);
            }
            XSSFWorkbook hssfwb;
            hssfwb = new XSSFWorkbook(OPCPackage.Open(tempSavePath));
            hssfwb.CreateSheet("casevalidationsheet");
            return hssfwb;
        }

Can someone please help me understand why NPOI is ruining the alignment of my excel workbook?