Bucket's annoyance is something I'm pretty sure many McDonald's employees also feel.
Maybe I've just been lucky, maybe I don't go to McDonald's that often, but I have never had issues with the ice-cream machine. It has always worked, the ice-cream was always great, and I have no memory whatsoever of ever having issues with them. I wonder if this is due to me living in a different country, as most complains I see come from US and UK residents, or maybe it just happened a couple times and then the story blew out of proportions.
Leave the real reason in the comments, I'd like to learn about this.