If you follow the recommendation to have the group come up with their own agreement on cooperation, this will make it easier to deal with any failure to uphold the agreement because they will have a feeling of ownership over it. If participants refrain from criticising others in order to avoid making anyone feel uncomfortable, I like to leave time for the frustration to grow so that the pressure to voice criticism becomes greater. You should also consider creating space for expressing criticism, either through introducing/collecting open issues or extra time for coming out of the workshop at the end of the day where you would ask about any difficulties related to teamwork. Additional encouragement can come from a comment/criticism by someone from the team about the disruption of not sticking to the agreement, while further pressure can be applied by proposing to do away with a rule, seeing as we have no intention of upholding it.
