I have the same problem.
I figured out that when you change the name of the game in LB, the video don't autoplay.
For example in my Commodore Amiga Section:
When I name the game "James Pond" the video Autoplay run smooth. When I changed the name to "James Pond: Underwater Agent", the video don't autoplay in LB.
In Big Box it works fine. Any Solutions? Thank You
Edit: Oh just now, I find out that you have to rename the Video the same like the Game in LB. Like rename it to "James Pond: Underwater Agent".
Sorry i dont wanted to disturb 🙂