AI video characters drift because each shot is generated on its own, so small differences in face, hair, costume and light add up. To keep one character across a film, fix the character before the film: approved reference images of the face and costume, the same written description in every shot, the same light per location, and a still frame approved for every shot before any video is made. In Reigniter's Cinema Studio the cast is kept as its own record, so every shot is built from the same approved character.