Issues are moved from one Sprint to another even when the Sprint Is not completed (the issues not in Done status either move to Backlog or other chosen sprints when completing the sprint) and data is lost.
The problem could be that the Board used are Kanban boards which does not support the functionality.

The sprint ids also got lost in the project once the sprint is closed and says you do not have permissions to view the Sprint or it does not exists anymore.
Please be so kind to share your suggestions on the sprint/boards issue in JIRA and let us know if there are any changes made to the boards in new releases?
Please let me know if more inputs are required from my end in order to make the issue more clear?
Thank You!!