error when trying to move DVD files

[special]

wurm wrote:
I should have clarified. I was using the DVD Player app/program on the Mini, not a physical DVD Player.
...

Understood, both the macOS DVD Player App and the stand alone hardware box will try to plough through several corrupt bytes and play and play... if the error is too bad, it will eventually give up.

Did you try my suggestion to copy the files to another location on the same hard drive?

Or can you rip a fresh copy?