Background:
I am the PM / Scrum master in a development team, we follow a semi-agile framework for app development. The team (which is newly formed) consists of 3 developers. I am not the line manager of the developers but only the PM/Scrum master.
Problem:
There is a developer on the team (let's call him Tom) who is constantly missing out on his deliverables. Tom, for example, delivers only 70% of the story points that were estimated at Sprint planning. Those were the stories that he personally estimated and volunteered to take on during the sprint planning session.
Analysis:
My analysis is that he is capable of delivering 90-100% of the story points however he has not been engaged enough to work on this.
Evidence - I sit close to him and notice that he spend a large amount of his time doing 'lesiure stuff'. We are in the Tech department of a MNC, there are barely any overtime so the average productive hours is about 7 hours per day (minus9 hrs minus 2 hrs of breaks). The amount of leisure hours he spent is close to 3 hours per day (outside the 2 hrs of lunch+tea break time).
For these 3 hours, he would walk around the office and discuss anime with the other colleagues, or watch downloaded movies, or do online shopping. It is only at the last few hours of the day then he would only sit down and rush to finish the work.
Question:
How do I manage such a person? The department itself has quite a relax working culture so I don't want to be the person who is creating conflicts unnecessarily. However, I am worried that he will spread his working attitude to the other team members who are so far still performing. Tom's coding skills is considering slightly above average and is more experienced than the rest of the team. He can rush his code pretty quickly (completing 70% of the deliverables despite working for only slightly above 50% of his time) so I also don't want to let him go.
Additional info: We are in the Tech department of an MNC so salary wise it is not as competitive as big Tech companies, but it is at least market median or if not slightly above it.