We often clone issues and move them to other probjects, where the sprints to not belong to the boards, but currently it isn't possible to exclude the sprint field from cloning. This would be the best solution, since a sprint is planned within the sprint planning and is not used for defining by reporters.

The next problem is, that currently it is not possible to remove closed sprints by editing the issue. The only workaround provided by Atlassian is to use the bulk operation and remove the sprint id. But this is just a workaround and needs to be handled with care.

Please improve the clone operation and offer an option to purge the sprint field, similiar to the option to include attachments or links. This should work, even when the sprints are closed alread, becuase the clone is a new issue.