De-sexed bun pooping everywhere

Gday all. Lucky is de sexed and is litter trained (he was at least haha), however he is pooping a lot (more than 50%) outside his box since I decided to change his litter box to a higher one to prevent peeing over the edge. The positive thing is that his droppings are near his hutch area which is where the the litter box is and not else where around the house as he is a free roam bun.

So it's been a month since the change and there has not been any improvement in his droppings in the box. Typically I'd wake up in the morning to a whole heap of droppings that is around a hand full or 2 worth which I then put it into the box. Through out the day the droppings also accumulates.

Any ideas on how to solve this issue would be great!

Since the droppings are around the box and not everywhere else, it sounds like it's more of a lazy bunny issue than anything else. How high are the sides of the new box, and how big is your bunny in comparison? My suggestion would be to cut a lower entrance on the front side of the box since he just seems reluctant to jump into it unless absolutely necessary (like for pee)