Thank you so much, Bartoz, for your investigation and clear answer to my problem.
With this knowledge, I can easily change the naming convention on my files.
(The reason for my late reply is that, even though I checked “Notify me of follow-up replies via email” I didn’t receive email alert of your answer.)
I am very please with your response that gives me a simple work-around to my problem. I will take my troubleshooting site down now that the issue has been resolved.