Thank you for providing the snapshots.
From the shared snapshots, I can now clearly see the problem as mentioned in your original post. At the moment, I am not certain what could be causing the said behavior but it seems to be related to the regional settings or the Excel version. We need to thoroughly study this case on our end to provide any further justification.
Please provide environment details of the machine on which the problematic XLSX file was generated. We are interested in the following,
- Operating System version
- Operating System Architecture (32bit/64bit)
- Service Pack
- Target .NET Framework
- MS Excel details (version & Architecture) used to view the result
After acquiring this information, we will move forward to simulate the environment in order to replicate the problem. In the meanwhile, we will also discuss this matter with the development team to get an insight of the problem, if possible.