off the rails

1. In an abnormal or malfunctioning condition, as in Her political campaign has been off the rails for months. The phrase occurs commonly with go, as in Once the superintendent resigned, the effort to reform the school system went off the rails. This idiom alludes to the rails on which trains run; if a train goes off the rails, it stops or crashes. [Mid-1800s]

Example Sentences

The film takes time to explore their history before things go off the rails.

From Los Angeles Times

But Kennedy notes that its rise tapped real anxieties: “People were right to ask what’s in our food, what doctors are prescribing us. That curiosity is healthy. But without real journalism and fact-checking, people went off the rails into diets and wellness snake oil.”

From Salon

“He is off the rails,” a member of the press pool in attendance at the Kennedy Center told me.

From Salon

The term “Ugly Cakes” — rendered in all caps, with evident disdain — was the author’s catchall for what she saw as a style gone off the rails.

From Salon

We’re going off the rails on this week’s Slate News Quiz.

From Slate