This mix up, concerning the investigation of Russia’s involvement in the US presidential election, was heard on NPR. It’s a mashup of “off the rails” (in a state of disorder or chaos) and “hit the fan” (become a scandal). Not sure which idiom the speaker intended, as both could fit in context. Perhaps the speaker had a mental image of the hobo catching a ride on a train and “hitting the rails”. A tip of the toque to JoErin Mahokey for hearing this one and passing it on!
P.S. Yvonne Stam, frequent contributor, added this additional explanation: “I would offer ‘hit the wall’ (reach a point of exhaustion) and ‘hit a wall’ (unable to make further progress) as well.” Agreed! Thanks Yvonne!