Some think it might be due to the material of the translucent covers, but apparently they also split between the opaque frame and the main part of the cover.
Not sure though if only covers with translucent are affected. I already have my second one, and it starts to crack again and also to make a wave near one button, so I am afraid I may need to replace it as well sooner or later.
So far I think all the pictures I saw of broken covers were translucent ones, so maybe the opaque covers hold better. But I don’t know that for sure.