Just discovered this today after logging on the first time after last week's update and discovered the following bug:
When I command a cart and drive past another, unused cart, the unused cart's wheels move in accordance to my movement: when I move forward, they show forward rotation, when I move backwards, they show backward rotation. So it seems the client renders the movement on all visible carts, not just the one I am currently embarked (I only have one other cart to test this with, though, and no commanding alt).
I'm certain this hasn't happened before last week's update.