PC Class 20: Session 6e10 -- Red Signals Prevent Completion

Here's another case of a timetable session that cannot be completed due to a red signal. Actually, in this case, multiple red signals.
When this session starts, the player's freight has to wait at a red signal because a passenger AI has the right of way. Once the signal clears to yellow, the player can proceed, but encounters a series of upcoming yellow and red signals along the line. As I drove, I occasionally checked the 2D map: the passenger was the only train ahead of me.
Then, at a certain point, a red signal stopped my train and remained red. Here's why: another freight in the block ahead that is also stopped by a red signal. Where did this train some from?

After waiting a while, I checked the 2D map again. The passenger had proceeded ahead to a distance that should have allowed the AI freight to proceed, and then my freight. But that didn't happen. So, I climbed down from the cab and walked along the track to the AI freight. Here's what I saw:

Had the leading freight's driver gone to lunch? or perhaps to look for a portapotty? or maybe just quit in disgust?