What if the interviewers in the group interview start to argue?

Argument in any work setting is not unusual. Pay attention to all perspectives. If you are asked how you would resolve the issue, make it clear that you understand all sides presented before offering your solution. Try to make your solution address as many of the issues as possible. It is okay to agree with one or more of the positions. The important thing is to show your respect for all the ideas presented in order to demonstrate that you will fit well with the people involved.