Hi Harish,
I don’t think it has to do with any caching plugin on my server but rather core functionality within WordPress. Have you tried to replicate the issue in your own instances?
To replicate, add a download/version and save. Load the public site and verify that the download is listed properly (using a form that displays the file date). Then, edit the version and change the file date and save. Reload the public site, does the download reflect the new file date?
Thanks,
-Craig