Is it difficult to communicate with this person?
Whether you’re interviewing for a job or starting a new relationship, red flag number one should be if you are having a hard time communicating what you mean to this person or if they aren’t communicating in a way that makes sense to you.
After all, If you're unable to have substantial conversations with your boss and co-workers, either you need professional help, or they do. It's not personal, it's business. Either way, it’s not going to work out.