Problems with team members can be very tricky. Sometimes you have to address it with the individual person. However, if things have escalated and are beyond that control, you would definitely want to take it over to a supervisor or lead of some sort in order to get some assistance in managing the situation. Usually, hopefully it can be managed between the two individual employee team members, but a lot of times an individual does have to go to management in order to get some assistance and or guidance on how to address the situation.