Symptoms

• When a user without the schedule issue permission edits an issue (using the Edit Issue dialog) or transitions an issue via a screen,
• If the screen includes the sprint field, and the issue is currently assigned to an active sprint,
• Then the issue is dropped from the sprint.

Work-arounds

• When editing the issue, use the Inline Edit functionality.
• Remove the Sprint field from transition screens.
• The change history of the issue should show if the issue has been accidentally removed from the sprint, and by whom.