I had the same problem, though it was one DVD in a set of 6. I didn't bother to check the buttons, since they had worked before. I was not using animated buttons.
My issue was with a specific file and the template, I don't pretend to understand the connection, but the bad buttons happened twice. The first time I thought it was that PC had rebooted before completing the burn. The second coaster had me investigating.
I didn't use the template I had created from the default, but located one of the others where the buttons would work--not all of them worked. I modified the operative template until it had the appearance I wanted, going back and forth between each change to make sure the buttons still worked. It was successful, the DVD plays, the buttons work.