For Sprint 5 of our project, Monster Truck Alley, I had to pull my team together and get them to tell me about what they're doing. Two group members are very close, performing many tasks together and making sweeping changes to the game's assets and code without informing me, the team lead, leaving me in the dark about what needs to be done and any issues that have occurred. This sort of behavior culminated during a formal playtest day, where the build we were presenting was broken and unplayable, while two days earlier I had seen it be completely functional.
In order to prevent this from happening again, I have attempted to secure the team's tasks and make them be more transparent about what they are working on at the current moment, and inform me of changes to that or ask me to assign them new tasks instead of nothing at all. I feel that my team should have already been doing this, but earlier attempts were met with middling and muddled agreement, with no follow-through. Now that we are nearing the end of our project timeframe, I feel that this rejuvenated approach will help push out a better product.