News Power created a pattern based on those 'big shoe' Sonic dolls that had really massive but fat feet. They tried this right at/before Sonic Adventure, and tried to brand him as such, even though that would have required green eyes. (notice he is a darker blue like SA, not lighter like classic)

Like the 'big shoe' dolls, they also used a type of plasticoat fabric to make the shoes shiny/fancy looking....however because the material wasn't 100% quality at the start, it didn't age well. The crackling you see at the top occurs whether the doll is stored properly or not. Sometimes conditions can trigger it early but it depends on the quality of the fabric the company chose most of all.
At left, you can see a fan fix for the problem. The coating was scraped off & red fabric paint was used to re-color the now all-white shoes. Since it wasn't 'puffy paint', but rather a matte non-plastic based paint, the doll shouldn't have the same problem to re-occur in the future.