Jump the rails
Definition 1 of 2
Pro Tip 1/3Negative Connotation
Implies an unexpected negative turn in events or plans. 
Our vacation jumped the rails when the storm hit.
Pro Tip 2/3Metaphorical Usage
Used metaphorically to describe plans or processes that fail. 
The negotiations jumped the rails after the disagreement.
Pro Tip 3/3Conversational Tone
Common in spoken English and informal situations. 
It seemed like an easy task, but it really jumped the rails.