I'd say I'm down 3-4 thousand this year from crazy/alice adventues/ dream catcher etc - but i love the wheels and have no complaints.
My opinion is just based on what I feel/have seen having played it for hundreds of hours. For me there's only two explanations.
They have a brake/ a way to give the wheel more momentum.
Or, there's a kink in the wheel. Maybe its imperfectly balanced but in a way which only manifests at a certain speed, certain section - sometimes.
I can't deny I have seen it jolt into an unnatural slow or somehow keep going. Why that happens - we can't know.