It is common in the early stages of Scrum implementation for there to be misunderstandings about what User Stories are for and what makes them useful. A ScrumMaster’s task is to be able to help the Team and Product Owner when they are faced with ineffective User Stories as they go into Sprint Planning.
Read the complete article here: https://agilepainrelief.com/notesfromatooluser/2019/01/deal-with-bad-scrum-user-stories-as-a-scrummaster.html