The engineering team at a multi-national retail company is deploying its flagship web application onto an Auto Scaling Group (ASG) using CodeDeploy. The team has chosen a strategy of a rolling update so that instances are updated in small batches in the ASG. At the end of the deployment, the ASG has five instances running. It seems that three instances are running the new version of the application, while the other two are running the old version. CodeDeploy is reporting a successful deployment. As a DevOps Engineer, what is the most likely reason that you would attribute for this issue?