Lessons From Coaching: Getting Tech Teams to Play as a Unit

Coaching makes it fairly obvious that giving everyone the same advice doesn't work. One person needs a specific correction; another needs enough space to try again.

A development team needs that attention too. If two people keep duplicating work, telling them to collaborate better is thin advice. Check whether they know who's doing what and whether there's a sensible point to compare notes. I'd start there before adding another team meeting.