My 12 year old dog is suddenly pooping in the house.... He does it either late at night or early in the morning. I took him in for a full physical, ran numerous tests, but the Doc said he was in great health. I think it is behavioral. He knows not to do it. I have tried positive reinforcement when he DOES go outside. But he won't stop doing it every night!!!! I have this vibe that he is angry about something. He is actually my parents' dog and I have been watching him for the last 5 months as they had to tend to family health issues. Does he miss them? Why is he acting up and how do I stop it? Thanks!