Generally speaking, it should be a quality problem, but it also depends on the use. For example, if unqualified shoe polish is used, insolation will also lead to leather cracking, and washing or soaking for too long before wearing in rainy days will also lead to rubber opening. If you think what you use is ok, go to the merchant and see what they say. If they shirk, they can call "123 15" to make a complaint!