off the rails

Idioms  

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]

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Example Sentences

What followed was an England rollercoaster ride that threatened to come off the rails.

From BBC

That has been enough to keep the deal from going off the rails already.

From Barron's

On Sept. 5 in the Oval Office, he went off the rails talking about grass, saying he’s planning to “re-grass all the parks” and that grass lives a life “you won’t even recognize because in a year that graffiti will be gone.”

From Salon

Network Rail has invested heavily in safety measures since a Glasgow-bound train came off the rails at Carmont, Aberdeenshire, after it hit a landslide following heavy rain.

From BBC

If you’re fortunate enough to have a stockpile of miles and points, judiciously book a backup flight in case your trip goes off the rails.

From The Wall Street Journal