I've tested all of the Z level locations I've come across and they all act the same. I've probably tried using Z levels at at least three different locations.
I've looked and nothing is corrupted.
I've realized why it doesn't work. I wasn't pressing Z to travel to a new level, I was hitting the contextual prompt on screen that should let you travel between Z levels. I do this occasionally when playing and it has worked properly for other actions so I just assumed it would work for traveling between Z levels as well.
If i press the z key on my keyboard everything acts as it should.
Would you still like to take a look at my save, Artur?