Its quite likely due to the leather quality which differs from season to season, hence the wrinkles in this bag.
I got 3 Chanel 19 n I could tell that they all differ in the thickness, smoothness , poofiness n quality of the lambskin . I noticed Chanel has this badass attitude to use the slightly "thinner" quality lambskin which makes it more susceptible to wrinkles for their more popular colours like my caramel colour , a very popular colour that gets repeated over many seasons. I got the later season caramel and the lambskin appeared thinner n more wrinkly. The first caramel must have been the 21 P season where I saw over social media, the lambskinbin this bag is that thicker, poofier n so so smooth , without wrinkles.
My best quality lambskin leather must be my dark grey colour which was introduced first time by Chanel , the leather quality is thicker n poofier n unwrinkled. Black another very popular colour is where there could be wide variations in the quality of the lambskin depending on the seasons. Chanel knows these highly sought after colours gets sold regardless of the quality of the leather
How I store my chanel19? I have them lying on it's back after stuffing the chains inside n together with the packaging papers to prevent wrinkling. So far the quilts at the back are alright