First, I couldn't believe he was admitting this to me and the customer in the middle of the project. Second, I couldn't believe the customer was paying him good money to help with this implementation. Third, whether or not the problems are within your direct sphere of control, there are things you can do. If you're the technical person leading projects where more than half the nodes fail, then it's your problem! You need to take the bull by the horns, figure out what is breaking, and implement processes, procedures, and documentation to fix it. No one should accept big failure rates.
Good management makes it happen
The older I get, the more I realize I can't do it alone. I know how to secure a computer and a network. But it takes more than technical expertise to work on a companywide project lasting weeks or months. That takes good project management. Insist on it.