In Agile project management, velocity refers to the amount of work a team can accomplish in a set time period1. When a project manager observes lower velocity and a high volume of tasks in the testing queue, it indicates that the team is facing some issues that are affecting their productivity1. The project manager should work with the team to understand and solve these issues12. This could involve identifying bottlenecks, improving communication, or adjusting workflows2. It's important to note that adding new resources or increasing the sprint duration may not necessarily solve the underlying issues and could potentially disrupt the team's dynamics23. Therefore, the best course of action is to work with the team to understand the root cause of the issues and find appropriate solutions12. References:
https://www.scrum.org/resources/blog/agile-metrics-velocity
https://www.clearlyagile.com/agile-blog/increasing-your-scrum-teams-velocity