My dog recently started pooing and peeing in the house, even though she is trained to do it outside.
This is not occurring everyday though, its only now and again, not sure why she is doing this.
There not been any changes to her life style or change of diet.
Any answers??
She is a Staffordshire.

Is she doing this while you are away or while you are home? Sometimes it's hard to remember that dogs need bathroom breaks just like humans, some days it's more than others. Does she give any signs that she needs to go out doors? What is her routine like now?

Completely eliminate the smell (even after cleaning dogs can still smell traces of the urine as they have better senses of smell) use eucalyptus oil it's a disinfectant and has a very nice but STRONG smell