My computer only plays movie trailers on some DVD's, with backup software it only shows the movie trailers not the full movie. My computer has played and copied other DVD's just fine. As far as I can tell everything is up to date for software. I'm running a dell XPS 8500 with win 10 ,16gb memory and an Intel(R) Core(TM) i5-3450 CPU @ 3.10GHz.
What are you using to watch those DVDs? Are these normal DVDs from a store or something else?
It may be an issue with your player and the security the DVDs use. Some combination of DVD players and playback software can have issues reading the protection.