Mario will not walk by an area he has accident--cleaned or not. I learned to take him for a walk in the house on his leash, past the problem area while praising him for doing well on the leash or doing a trick near that area. Then he knows mommy is not mad, and all is well in his world. Then he no longer avoids the spot.
This has worked in my favor when at my in-laws though. Their dog made a mess in the house, and Mario was being blamed, but I knew it was not him since he would go past the area
