Intermittent black screens during slideshow

Environment: LrC 13.1 Mac Mini M2 Pro Sonoma 14.2.1

I created a slideshow collection over over 1,000 images (!) each around 50MB (Fujifilm X-T5 Raw) and pressed preview and just got a black screen. I switched off graphics acceleration and restarted LrC but that didn't fix it so I turned it back on. Then I tried previewing another collection of around 20-30 images and that worked fine. Then I tried the large collection again and this time it started but after every few slides the screen went blank for a few seconds and then continued. I'm guessing it's something to do with the number and size of images. Appreciate thoughts from anybody. Thanks.