The project manager should review the user roles and update the team charter to ensure that the project team members have clear and balanced responsibilities and expectations for each release. This will help to improve the team performance, collaboration, and accountability. Documenting the risk register, speaking to the customer, and involving the product owner are not directly related to the problem of uneven workload distribution among the team members. References:

PMP Exam Content Outline, Domain II: Process, Task 2: Manage project artifacts and ensure they meet the needs and expectations of key stakeholders.

A Guide to the Project Management Body of Knowledge (PMBOK Guide), Sixth Edition, Chapter 9: Project Resource Management, Section 9.1: Plan Resource Management, Page 313.

Professional in Business Analysis (PBA) Certification Exam Outline, Domain III: Analysis, Task 3: Define Requirements Architecture, Page 13.