I have an 11 yr old standard Dachshund that has been using a dog door since arriving at my house at 8 weeks old. He has no known health issues (vet checkup 1x per year). Recently he has started balking at coming in the dog door. I'm not sure if it's a game or if he's having some physical issue with the door. With enough encouragement or the right incentive he goes through, but increasingly he just stands on the other side and barks. Or sticks only his head through and barks. Nothing else in his routine has changed. I've inspected the dog door and it is working perfectly with no sharp edges or other apparent defects. I'm concerned that winter is coming and if he refuses to enter the house while I'm at work he could become quite uncomfortable in the Colorado winter. Anyone have ideas on how to understand this change in behavior? Thanks for any thoughts on this puzzle!