You'll want the owner present to manage tenant behavior.

What is the behavior of the other agents in that office (work from home, in the office)? 

There is no excuse for that type of behavior, especially over something minor such as changing locks.That being said, I don't understand what you expected to accomplish with the walkthrough given the facts you laid out.  

If that dog had tendencies of poor behavior it would not have been accepted as a police dog and 2. they darn sure don't go inside of any building, they are better trained beyond house broken.

Has she demonstrated responsible behavior since?

There is plenty of room for unethical behavior within that realm.

To over-simplify, I think screening is a great way to understand (a) are you who you say you are (b) do you pay your bills and (c) is your behavior worthy of this expensive asset?  

Also, I would make sure to communicate a little via email or text, so you can have some physical evidence of his behavior.

For all we know he had multiple affairs and that led to his divorce, so he has reckless behaviors that led to his financial issues.

You need to re-establish with the tenants new rules of behavior.