Hi, Deepa, my apologies for taking so long to answer your question.
I never did find a solution. Somewhere along the way, the problem cleared up. At first, I kept Windows File Explorer open so I could see if when a revised file failed to save. This kept me from assuming a successful save. Also, when I wanted to start from an existing script to create a new one, I started the practice of creating a new script file, then copying the contents of the existing script and pasting into the new. So the new script has a different create date and a different UniqueId ( a test script property) that Test Studio uses internally.
So, in short, I avoid using the script copy method (available on right-click on script name) or any copy/paste of script files.
Hope this helps!