Image grid skipping 1 spot Options

[Dragolin]

Hey guys

I'm adapting a page, it used to run quicksand plugin to sort the image grid, but I don't need sorting anymore. So I disabled the Quicksand jquery.
Instead I'm only using the grid design in combination with lightbox2 to show the complete galleries per topic.

However it skips the 7th spot in the grid and continues at 8.
Funny thing is that when I use the Firefox element inspector, the image jumps back into place. So I can't figure out why this is happening. The spot is just empty.

Would appreciate any feedback

Link: www.ddw.be/#foto

In this 2nd section called 'realisaties' you'll see that the 'ventilatie' comes in place 8 and not in place 7 (after warmtepompen)