Have there been cases when tasks were suddenly reprioritized in the middle of a sprint and everything had to be redone?

Yes, such situations have occurred. During the middle of a sprint, when there is a sudden reprioritization of tasks, it is important to adapt quickly to minimize the loss of time and resources. Usually, I review the current plan, discuss with the team and the Product Owner to understand the reasons for the changes and determine which tasks can be postponed or redistributed. It is important to remain flexible and maintain transparent communication so that all participants understand the new priorities and can effectively reorganize their work.