Scrum practitioners:
What is your experience with the degree and the right time to "negotiate" on a story? Is this done purely during PBR, and when a Sprint begins, the story becomes"fixed?" (Even though it's not supposed to be "a contract?") Or during development, as collaboration occurs, does "negotiation" also occur? I'm sure there are risks to being too strict either way....
If you allow "too much" negotiation during the sprint and are always negotiating about what can or can't be accomplished, it could be that: