The fact that it reads some DVDs and not others does not indicate a need for a firmware update.
The reader and burner in a CD-DVD player is a different head for the CD and DVD as well as the the burning lights. Thus it is possible to loose the DVD and still have the CD operate. Usually it will be the DVD that goes out first.
Your descriptions indicate one of two things....dirty laser or dying laser.
Invest a few dollars on a DVD cleaner disk (has a small brush on a DVD to brush the reader/burner clean of dust. If this fails to fix the problem, then it means the DVD reader light is dying. If the cleaner allows even one of the unreadable DVDs to read, then reclean...could require several cleaning to totally clean the light. If the light is dying you will see more and more DVDs that used to play no longer recognized by the drive.
FYI - All files on a movie DVD will be in the Video_TS file...The Audio never contains files. Someday when I got time I'll explain the file setup and how these separate files combine to play a movie.
