An exploit that basicly allows anyone who knows anyone with rare to eventually get as many copies of these rares.
Why is it problematic? Because :
-It makes rares very rapidly become non-rares, for the ones using this glitch
-It makes people using it get a (heavy) advantage over those not using it. Which is the definition of an exploit.
Possible fix : no spin in pvp / rares are transformed in relics for pvp.