I realize that its been 2 1/2 weeks and you've already solved it, but I thought I'd add my two cents here. Its natural to think of the problem as occuring in a flat and empty plane, but in reality there may be obstacles in one's way that could prevent movement in a direction, or you may be moving along up or down. So, N, W, S and E could, theoretically put you on the other side of a wall or cliff, or directly below where you started. That is why you can only cancel opposites that occur within the same groupings of movements within the same plane that are not interrupted by perpendicular movements. I hope this makes sense!

I do find it somewhat ironic that you used code which obfuscates the action in a function called 'humanReadable'

Not a dig or a criticism, just an observation 🤓