What could sub-groups improve when interacting with others? Source:
Identify sub-groups within the participants that interacted during the iteration, e.g. developers/testers, clients/providers, PO/developers, etc. Give participants 3 minutes to silently write down what they think their group did that negatively impacted another group. One person should be part of one group only and write stickies for all groups they don't belong to - 1 sticky per issue.
Then in turn all participants read their stickies and give them to the corresponding group. The affected group rates it from 0 ('It was not a problem') to 5 ('It was a big problem'). Thus you get insights and shared understanding about problems and can select some of them to work on.