If the problem is the body instance array then there are three possible reasons why it isn’t getting filled. In the function PaperGroupedSpriteComponent::SetupNewInstanceData(), it creates the body instance when “(bPhysicsStateCreated && (InSprite != nullptr) && (InSprite->BodySetup != nullptr))”.
So either you’re adding the sprite instance before the physics state has been created, the sprite pointer you’re passing in is null, or the sprite you passed in doesn’t have a body setup. Figure out which one it is and we can try to fix it.