The safety system fails because the trains are no longer in a safe position. You need to have them in manual mode to move them to a safe position to be able to start the safety system again. The manual override is the recovery, if you want to wait, you are going to wait for eternity. However the issue this ties seems to be, that they did not place the system into manual mode, when they should have. https://news.ycombinator.com/item?id=50298796