Derailed, of a railway carriage, etc.
Away from the proper subject; irrelevant, unrelated.
Not on right course; inaccurate.
Source: en.wiktionary.orgI was the conductor of the Underground Railroad for eight years, and I can say what most conductors can't say; I never ran my train off the track and I never lost a passenger. Harriet Tubman
Otherwise we get off the track and we do not fulfil the historical role which we want to fulfil: to help the masses, the exploited and the oppressed of the world, build a classless society, a world socialist federation. Ernest Mandel
I would step into a place of being lined up with a sense of purpose and my inner compass, and everything was going in the same direction. Then I'd get lazy and get off the track. And then things would start to fall apart, and I'd back up and get it together again. Kathy Mattea
Once you begin to fall off the track and believe you breathe different air to everyone else, you're doomed; you're finished. Anthony Hopkins
Afterwards, upon replacing a damaged tire, the car started up and was driven off the track. Source: Internet
But the Red Bull careers off the track and Button keeps his place. Source: Internet