So I made a train thing yesterday.
It currently uses the code from the Hazard Train by Swollow, which has this same issue, bit it's less noticeable because it's smaller.
The model is perfectly straight with all the scaling done correctly etc.
This is how it looks:
Looking towards NORTH

So this is completely fine, and there are no issues when the train is moving north
Looking towards EAST

It looks rotated a bit, but it still moves straight along the brick grid
Looking towards SOUTH

Same issue as east but less severe
Looking towards WEST

Same issue but it's even less
What causes this, and how do I fix it?