We just brought this up with our trainer. The dog was doing great for a few weeks and then recently relapsed back into peeing in the house. The trainer was not a proponent of punishing the dog when he goes in the house. Apparently, that makes them feel guilty when they go inside or outside. They don’t know the difference. You can only consistently reward them DURING THE ACTION while they’re going outside. And more importantly, don’t give them the chance to go inside. Take them out as frequently as possible and put them in the crate when you can’t watch them. That was his advice and it’s working out for us.
In general, there’s going to be accidents for the first few months though. That’s been my experience with all my puppies.