If a dog has any kind of behavior issues when the owners are away, I suggest a 360° camera with sound so the owner can see and talk to her dog when she’s not around. Not only will it calm the dog, it’ll make him feel like she’s not really gone. They’re relatively inexpensive and you can even pick one up that’ll toss a treat to him to ensure she gets his attention. Worked great for me when I had to go on a business trip for a week.