The dog's needs are not being met,
Will you be able to get the owner to face up to the reality that they are unable to meet the dogs needs?
Doubtful, as they clearly got the dog to meet their own needs, without considering what the dog required, they have not manage to provide the necessary training, socialisation,stimulation and exercise, if the dog's needs had been met, their would be no problem,
Will they admit that to themselves and address the problem, it's a lot of effort, which is why they have the problem.
you live below someone who puts their own needs before an animal they have taken on responsibility for, so you have to make sure that you get them to prioritise the issue,
Explain that it has to stop, either meet the dogs needs, or find somewhere else to keep the dog when they are out, or you will have to go down the legal route, you are dealing with people in denial, so good luck
I feel very sorry for the dog.