You're not going crazy! I can confirm that, for me at least, both the picture cube and the slideshow, which I prefer, are misbehaving.
As well as Picture Cube's unwillingness to update, Slideshow is often showing images upside-down, and also often over shoots on a slide, showing neither one nor the other. It's been that way for a while now.
In both examples below, the cube has come to rest and is displaying a slide, or at least, believes that it is doing so.
A fix by Saturday would be a long shot to be honest.
I'm not sure if it will work for your party, but you could try adding the pictures to the audio playlist. When you kick off the playlist, the audio will play, and the pictures will display fullscreen. When started in this way, the player controls will control audio playback. Give it a try and see what you think.
-marko.