Great question! In essence, the bags are soft-sided duffels, and by design all of the sides are semi-pliable. When creating the bag, we were seeking a balance between durability and light-weight. Sure, we could have designed them to be built like tanks, but the empty weight would simply, then, not be acceptable!
That said, if the long side of your bag has bent, simply push it back into proper position, and you'll be good to go! As long as the sides are not repeatedly bent back and forth, they will retain their strength. IF the side support has somehow broken, please email us at firstname.lastname@example.org with a photo and your order number, we'll review, and we have a fix for that as well.
To help prevent the sides from bending in the first place, here are a few ideas that may be helpful, but are not meant to be an exhaustive list: please do not carry the bag on your side, where it might be resting on your hip. Instead, use the handle on the top of the bag (opposite side from wheels) to carry the bag vertically. Also, be careful when loading in/out of your car. Airline travel could also cause this, as the baggage handlers are not gentle. We think it's absolutely adorable when we see photos of little dancers sitting on or playing inside the bags.. but this is a BIG NO-NO! Our bags are not designed for this, and this can also lead to the sides bending or breaking.. and more importantly, it's a safety risk, so please don't do it!