Things go wrong every now and then! That’s about as accurately as I can put it unfortunately. There’s a thing called the “Bathtub curve” which basically says that products go wrong the most at the start of their use and once they’ve gotten too old. A lot of our equipment is coming up to the end of their design life so things breaking are becoming more frequent! Almost all of the things that go wrong are a small component like a relay or resistor burning out after 30 years of use. We have a lot of equipment so maybe a new little thing goes wrong every few weeks.
That said, the JET experiment has had some interesting things break. Last year a piece of copper was hit with a particle beam which exploded copper everywhere and released a few tons of water. It’s all patched up now! Those kinds of events are very rare but make interesting stories.