Thanks for the detailed report and video. This black background during the transition is expected behavior for 3D-style transitions like Flip, Gallery, Box, and Cube — during the rotation, what you’re seeing briefly is the back face of the slide plane, not the slide’s actual background. There isn’t currently a setting to change that back-face color.
If having a white background throughout the transition is important for your presentation, we’d recommend using a non-3D transition effect (e.g. Fade, Push, Wipe) instead, as those don’t have this back-face rendering.