So, I called customer service to ask about exchange, but of course it’s never available and only return was possible. I sent them the pics and they returned to me next day saying that this is not considered a defect, since every bag is made by hand and is unique, but they have no problem with me returning it if I’m not happy.
I stuffed the bag overnight and now the sides don’t look concave anymore, so I guess I’m keeping it.

Interesting thing that even though the bag was produced last week (so definitely not a return) it came with the shoulder strap already attached.