Dubbing is off

I’ve been downloading and burning movies for a few years now without any major problems. Lately I’ve noticed that once I have the movied covereted and burned to DVD the dubbing is off, but when I watch the movied in it’s original format off my computer, the dubbing is fine. ANyone have any idea why this is happening?? I can only assume that dubbing ends up out to lunch during the conversion process?? ANy help or suggestions would be great!!