The puppy I had the most difficulty housebreaking always needed to poop twice. It took me a bit to catch on to that fact. I've also found my boys benefit from at least a short walk off property to get their innards moving. They are big and mature enough not to make messes in the house now; instead they get constipation when they don't get their proper walk. I try to make sure they get at least one long walk every day, sneaking one in between cloudbursts if needed, to ensure they thoroughly empty themselves.