Debate about the merits of joint session is unabated. Of course it may be helpful for the parties to meet, even if briefly, and a direct exchange of information is usually more efficient than by messages shuttled between rooms. But sometimes a plenary session can create more heat than light and leaves everybody eating their lunch and wondering when the real business will begin.
It may help to identify a specific aim or focus for that first meeting, even if only to identify and update issues and damages. However, in my experience the most important aspect of a joint meeting is tone, so that generally, if the parties believe they can have a conversation the meeting will be worthwhile. If it is more likely to be an exchange of lectures, then perhaps look for a different way forward!