hmmmm, heavy railcars, steep hills, what could possibly go wrong? Were there no redundant safety precautions for the brakes? Hmmm, let me see, gravity plus wear and tear, yeah, who woulda ever thought? Especially after the 1st time in 1915? Or the 2nd in 1926? Well, there was a repeat in 1947

Seriously, who could ever predict that the rained on greasy cables would be less than perfect for applying brakes to? 

https://opensfhistory.org/news/2018/07/23/tillmanys-ride-a-closer-look/