There’s an interesting quirk with the physics engine where assemblies will “fall asleep” if they have been motionless for too long. Unfortunately, the check to make sure the part should wake up is not that great, leaving the assembly motionless even though forces are acting on it.
I have two examples of things that are affected by this:
When the stop block is removed, the cars are highly likely to stay motionless, even if one cart has awakened.
None of these engines are able to awaken the 4th car away from themselves. On the track furthest from spawn, there is three large passenger cars, a tender and a locomotive. The 4th car will not awaken after it has gone to sleep no matter how hard the engine pushes it.
One of two things would ease the sadness in my heart:
a method to awaken parts
better force sensing (it seems that hinges are not well-respected sources of force in the engine’s eyes)