No, that's an accident. I fixed that now.
I have kinda found a solution; rather than getting the position of the main camera for the Y variable, I've got the position of the player spaceship instead.
This makes sense as the position of the main camera is actually driven by the position of the player ship in the first place, and the ship is rigidbody/collider using forces etc for movement, so it'll be a physics engine / fixed update thing.
I figured if getting the position of the ship returns the same value then that would work, and it seems to. It looks a million time better anyway.
I guess I should mark it as solved.
Thanks,
J.