My response to this question 9/10 times is no you do not bring in a new team. My experience is that if integration is failing it is due to many reason’s so difficult to believe a new team will solve the issues. Usually due to lack of plan, resources and expectations.
It’s hard to say without evaluating the integration in entirety. However, I agree with Marco, I would not bring in a new team unless it’s very bad. I would bring the current team together to reassess the timeline and goals and walk away with an action plan to get it back on track. Also, I would be sure to communicate challenges and any potential changes in dates or outcomes with appropriate parties. I would consider a new leader of the project before I would change the team mid-stages.
If integration is failing, first I would go back and look at a deal rationale. Do the integration team and affected stakeholders fully understand the final goal? The new team simply would not help in case of unclear deal rationale.