I find Wick’s litter box adherence drastically declines as the night approaches. I suspect it’s because he’s all riled up from the daytime naps, so he just wants to go around his territory officially and zoom around.
It’s always good to keep reinforcing litter box habits. You may want to choose an evening where you stay up a bit to observe if it is poop-flings or actual pooping outside the litter box — your bun may have come to learn that she can poop wherever if you’re not around or when it’s dark. It may also help to provide another litter box or two around; I find Wick is less likely to travel to his hutch litter box in the evening, so he has two additional boxes out in the living room.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.