How I describe imperfection and free will

You know when you go to the store and grab a grocery cart, and it has a messed up wheel? It's still up to you to steer but it is always inclined to go off, and it won't just move in a straight line. That's imperfection.

Your path will waver and you might hit a few things. But in the end you are still in control of the cart. That is free will.

Edited 2020-02-17. (I said "store" again instead of "cart". *facepalm)