ᐅ Ikea Maxima drawers do not fit?

A friend received an IKEA kitchen. She wanted to change the interior of the 40cm (16 inches) cabinet to have three drawers instead of two large ones, so she would also have a cutlery drawer.
We picked it up yesterday, and I was able to assemble the three drawers, but not install them into the cabinet because we had to leave. Today, she and a friend (both unfamiliar with IKEA assembly) are doing the installation, and the following issue has come up:

The three fronts apparently do not fit together properly.

I tried to explain that this is probably not an IKEA error since the interior fittings are standardized, and that a) it is either a mistake made during the drawer assembly yesterday (which I doubt, since the instructions clearly indicate where to screw), or b) they made an error installing the drawer slides.

What could be the cause? The bottom drawer doesn’t go all the way down, and there seems to be only one way to mount the drawer front. Could it be that the slides for the 40cm (16 inches) drawer are different from those for the 20cm (8 inches) drawer, and that a slide for a 20cm (8 inches) drawer was installed at the bottom?