Hello Kirk,
I've noticed that I can't start a slideshow in the latest PM version on my Mac Studio (Apple M4 Max) – see screenshot 1. The screen goes black, but the images don't appear. When I exit slideshow mode, the window somehow remains open and still shows up on the desktop/finder (screenshot 2).
On my MacBook Pro (M1 Pro) – also running the latest PM version – the slideshow works as expected.
Both machines are running macOS Sequoia 15.5 (24F74).