Well, don't know if anyone actually posted this up, but, whatever, I'll post it anyways.
Some weeks ago, I was building a friend's pali, and said, "Hey, what if I take 2 carts, if it's possible". It's possible, the thing is, one of the 2 carts got stuck with the other, leaving me to carry just 1 of them. I noticed something strange, and it was that basically I could walk/run normally as if I weren't pushing the cart, did it 4-5 times and it always had the same result.
So the bug is, you can walk/run with a cart if you pull 2 carts at the same time and let one get stuck with the other.