As a consultant, we often need to understand the painpoints, challenges and problems of various parties in the conversation. That is how we can add value to work on the problems, identify the solutions, offer the right recommendations.
The challenge to sharing painpoints or problems is there will always be some kind of resistance. It is difficult for parties involved to openly confess they need help; and the problems they identify at first may not necessarily be the fundamental problem. They might also be afraid that the problems identified traces back to themselves or some mistakes they had made before.
So what can we do? Reminder of the objectives of the brainstorm and objectives of the team. Walk through with the team what is the process they have at present to get from their starting point to their objectives. And ask them about the difficulties or bottlenecks at each step along that process.
Hope this general framework for a start contributes to your brainstorming!