I have a two year-old dog that was house trained. At night, he sleeps in his own room (door closed). This has worked out fine, but over the past few months he has sometimes urinated in the room (same spot more or less) at some point before we get up and take him out in the morning (around 6-630am). I am not sure why he does this sometimes and not others. He is never in his room at night for more than 10 hours, usually less. I try to clean the spot as well as possible, but he has recently done it again. We are nervous about leaving him out of his room for the night now because of this. Overall he is an excellent dog behavior wise and has never had an accident anywhere else in the house. Any advice?