The slide navigator in version 12.5 incorrectly shows half slides. To reproduce, I select a slide, go to audio and add an AI text to Speech with the Timeline showing. Then, I attempt to update the button on the timeline to show for the entire slide. Upon returning from this action the slide view shows only half the slide and a blank areas where the timeline shows. If you scroll the the slides up and down, the slides will correct themselves. See the screen shot with items in red. Other slides in purple look fine because I have not added audio.