I was always lucky in getting very reasonable people as my managers/clients until my company found this new project from a Bay Area startup. The client has following characteristics:
1. We have standup meetings scheduled twice every week. He doesn't show up in 90% of them.
2. He doesn't respond to most of the emails which are to get his feedback on latest development progress.
3. A week before the initial deliverable was due, he demo'ed the project to CTO. He didn't give me any heads up before giving the demo. Incidentally there was a bug in the system at that point and his demo didn't work as he expected. He expressed his anger by a one liner email.
4. On the day of first deliverable, he gathered his entire department to showcase the product. He asked us to run a flow which was neither mentioned in his requirement docs nor it was related to the core features due for the deliverable. Since we weren't prepared for the flow, it didn't work. He shared his anger later with my manager.
5. He'd agree to everything I present in initial requirements, and later get angry for something not even remotely present in the initial requirements.
The project is super complex and he is barely involved in the development process. I know I can technically face any challenge, but I'm struggling with locking down requirements and managing his expectations. I'm whole-heartedly committed to learning and adapt to this challenge, but I'm not been able to develop a mental model so far.
How you'd handle a difficult client like this one?
Why don't they show up to standup? Why aren't your emails a priority to them? Why was a demo to the CTO necessary or desired? Why did they leave you out? Why was that flow important to them? Why did they discuss something out-of-scope?
I only see your perspective. If you don't know the answers to these questions, why not?
Advice isn't going to help; you need a relationship manager. You probably need to bring someone in to get face time with this person, and handle them on an ongoing basis, again probably in person every time. It's going to get expensive. You're probably not going to make as much money on this contract as you expected as a result. This isn't a technical problem to be learned from and fixed; this is an interpersonal problem with someone who works and thinks differently than you, who is also unfortunately holding the purse strings.
The most valuable thing I learned working in consulting wasn't how to be a better designer or developer, it was how to handle relationships. I learned that the next time I went out on my own, I'd hire a business and relationship manager, and I would absolutely pay them 50% or even 60% of my earnings, because that is the "real" work of consulting.
A relationship manager will give you a list of signs that you shouldn't have taken this job in the first place. A relationship manager would have specified that this person's attendance in standup is either mandatory (and therefore in the contract) or not required (which means they wouldn't have even been invited). A relationship manager would probably have established up front how this person likes to work, and that probably means in-person, and would never have sent an email, and instead had lots of meetings. A relationship manager would have made sure you kept control of the demonstrations, so off-message presentations couldn't have happened, and would have made sure that out-of-scope things either didn't come up, or were quickly addressed by understanding why they came up.
Your takeaway from this will be how to better vet potential clients, so you can either not take their money, or add in the cost of relationship management to their contract. You'll also learn to write better contracts, that firmly establish the participation required, including penalties up to and including the termination of the contract with full payment and no deliverable, should the client violate their expected level of participation.