Some people (me included) have the innate ability to cause iron and steel to rust just by touching it. We're not talking "holes in exhaust" sort of rust, but still the action of rust forming. This is mainly due to your skin's oils which react with the metal.
The edges of the cups can get scratched up and be a bit abrasive (on your face).
i think this happened because your sticks were lifted higher than the string around your neck so it bouces torwards you Will.
so is it true that the circus hubs break easily?
is there any way to "save" a dented diabolo? mine starts wobbling like heck after i give it a good spin (and i'm pretty sure the axles aren't loose). i dont want to order another one all the way from taiwan... oh yeah and they're the rubber bearing fly diabolos.