Hi.
I forgot to mention that I used am image file already (.iso) with VirtualCloneDrive. This worked fine and all files were readable. However didn't consider this test as very reliable since other software drivers (VirtualCloneDrive) might have permitted proper display/reading of "burned" files.
... later ...
After rebooting this morning, the files on subject DVD-DL became visible ?!?!
I did multiple reboots after the problem occurred, but none helped to see the files. Now ... all of a sudden, it works. I didn't change anything on the system between posting the initial article and the reboot this morning).
No clue what went wrong here, but now it works.
Thanks for the answers!