I am familiar with these linkage systems. There are various designs and each has a functional variable. Some are designed into a complete linkage locking system, others are restraint systems only. There are static and dynamic factors involved, and of course loads vary significantly. Some of these devices have warning systems of various designs, which provide feedback to train operators and train yard workers as to the current condition of the system, and if the linkage is properly locked or not locked. If a holding device failed due to sudden acceleration (shock load) of the vehicle, as seems to be the case here, I would have to look at a few things to determine exactly how and where the failure occurred. This would involve the use of several different techniques: Finite Element Analysis could show the load capacity of this particular device, and of course documentation about the device’s specifications would further shed light on exactly where the failure occurred. I could easily ascertain proper design of this system, so strength of the system and materials in this particular system would be important. A failure of this nature is unacceptable, since this is exactly the kind of dangerous situation that these locking mechanisms are used to prevent.