On a complex project with a large degree of uncertainty, the team’s velocity is declining.

Conduct a spike so that the team can focus on defect repair without the distraction of new work items.

Create a burndown chart to ensure the team understands the variance between the current and target velocity

Work with the product owner to reduce the complexity of the work so that the team can improve quality.

Work with the team to ensure that acceptance criteria is being properly defined and understood.