IMovie DVD freezes in DVD player. Why?

So It's been more than 3 months since I got on this page, and I had this question up previously but I can't seem to reply. I clicked on 'problem solved' on one thinking it would give me options, but it didn't. So

just one last comment. I made life in photos dvds for friends and family for years when IDVD was separate from IMovie. Then they combined them. I learned the new upgrade thru Udemy. So with Toast the dvds would freeze at some point. Not the same points, and someone said DVD players are less forgiving than external super drives. One suggested I get a $14.99 burner on Apple. which I did. It did seem to work at first, so I made 16 of them and sent them out.....and some worked and some didn't. So I respect the people with more knowledge than I but it would seem to be in the IMovie when it combined the dvd burn into it....ok, I know it makes an mp4 but something is wrong. I finished this dvd of my late son's life and now I don't think I'll ever attempt another.