When the scrum team doesn't pull the chain

In the scrum meeting:
Hari : Yesterday, I was working on integrating the console with services. Today, i will continue to integrate. No blockers as of now.
Jagan : Sounds great. However, wasn't this be the case yesterday as well?
Hari : Yes. The story is complex and the UI implementation got some feedbacks of late which had to be implemented.
Jagan : Ok. Are there any revisions made in the screen?
Hari : The parsing algorithm done as part of sprint had introduced a fresh thought and these changes were requested.
Jagan : However, how can algorithm be done when its not a planned item?

This is a familiar situation scrum masters will come across particularly when the team is empowered to make decisions. Scrum masters should encourage the team to pull the chain and stop the production when the done criteria changes or when scope creep is tried.