Recently, I'm doing so research on the passively steered mid-axles of Leyland and Volvo Olympians.

Most bus fans agree that the mid-axle on a Leyland Olympian will be locked no matter what direction it is pointing at when reverse gear is engaged, whereas the mid-axle on a Volvo Olympian will be locked once it points back towards the centre when reverse gear is engaged. Those are what I believe as well. An ideal Volvo example can be found easily on youtube such as: https://www.youtube.com/watch?v=7GoDcOplexo (by fl3698). However, I could not find any ideal example for Leyland on youtube.

Now, let us look at the some counter examples.

The bus (it is tiger Volvo, determined by the license plate number) in this video shows something very peculiar.
https://www.youtube.com/watch?v=QqwCetL0vGI (by TONGCHANNEL).
All six wheels were on flat surface (by that I mean the wheels did not hit any kerbs), but Oh My Buddha. What happened to this Volvo? Why didn't the mid-axle turn back to the centre position?

And then there is another strange thing in the following video: https://www.youtube.com/watch?v=DejpllhUHgg (by PKD32).
When the CTB Leyland went in reverse, the mid-axle turned back to the centre position. Oh My Buddha. Why?

I'm so confused now.

It would be great if somebody can answer my question. Thanks.