Camera is charging atm, but I will try and explain better, because maybe it's something to do with how i put them on.

Imagine you do the snaps/aplix up so the sides meet in the middle. Then, what is left over on either side, on the front wings of the nappy (so underneath when it's closed) turn inwards to form another layer underneath where the nappy closes (under the belly button)
So instead of having the two layers (front and back wings) you now have 3 right in the middle and that pushes the front of the nappy outwards.

Gosh, I don't know if that helped at all. LOL

It doesn't happen on my IB or BBH, and I think that's because they both have two horizontal snaps.