Every unit will have minor gaps along the sides, they won’t be sitting flush along all the edges. This is not a manufacturing defect, but a natural result of the moulding process and how the material cools down after injection.
Rest assured that this does not affect the functionality and safety of the product. It is a cosmetic occurrence that we’ve chosen to accept in order to maintain a lightweight and more flexible product.
In order for the product to be lightweight, the outer walls have to be quite thin, which results in it being less capable of holding a 100% rigid, fixed shape after being released from the moulds.
However, this flexibility is what increases its ability to withstand pulling force, eg when kids grab and pull on the sides, it’s less likely to break because there is flexibility in the material.