The issue appears when there is a) an image playlist running (image/video cue with multiple images that play/repeat), and it is followed by b) a SFR cue to Fade Out and stop the slide show. What I've discovered is that when the video/image cue does NOT have a sub-cue Fade Out time coded, and the SFR cue is initiated, the SFR cue, and the currently playing image both get stuck and continue to display - the SFR on the main screen cue list, and the currently playing image on the main output screen. When this happened to me, I had to kill the program in order to get it to stop displaying, as Stop All did not work.
The problem is easily corrected by coding a Fade Out Time on the image cue once you realize what the problem is. But I ran into this during a first performance - and of course, I had just added the slide show that night, so the problem snuck up and bit me on opening night

Now that I know that I NEED to code a Fade Out time, I always will. But, I thought you might want to include code to avoid this problem internally.