Summary

If you have running parallel sprints from different projects that share the same board, issues in a sprint from Project A that are completed after the beginning of the parallel sprint of the Project B will be moved to the next sprint on the Epic Burndown report even when these sprints are parallel sprints and shouldn't be sharing issues at all.

Description

For example: You have a board "Atlassian" that has a filter including several projects. You go to the Epic Burndown report and look for an epic "Atlassian: Epic 10".
Now, you'll be able to track how many sprints are required to complete the epic. You'll look then for Team Green Sprint 27 and Team Red Sprint 27 that appears on this report. For this epic, only Team Green Sprint 27 had issues worked and completed on for this epic, Team Red Sprint has nothing to do with this Epic, but appears on this report as it's project is included in the filter for this board. These two sprints are parallel sprints.

Sprint's created and end dates:
"Team Green Sprint 27" 14/09 17:00 - 28/09 17:00
"Team Red Sprint 27" 14/09 17:57 - 28/09 17:59

Expected:
Issues would appear under sprint "Team Green Sprint 27" normally.

Current behaviour:
Issues are all appearing under "Team Red Sprint 27" even though they were never worked on this sprint neither have sub-tasks related to this sprint.

Cause:
In the "In the 'Completed Issues' table, why are some issues grouped into sprints that they are not assigned to?" question on this documentation: https://confluence.atlassian.com/agile/jira-agile-user-s-guide/using-a-board/using-reports/viewing-the-epic-burndown# it says that if an issue assigned to Sprint 1 is completed after the start date of Sprint 2, this issue will appear on the Epic Burndown report grouped with Sprint 2 issues.

So, given the create and end dates of each Sprint in the given example above, issues that were created on the "Team Green Sprint 27" sprint that were closed after 17:57 (create date of "Team Red Sprint 27"), were moved to the next sprint of the period that the issue was closed, in that case, "Team Red Sprint 27", even though this sprint is from a different project that didn't work with the Epic we're looking at.

However, this shouldn't work like this when you have parallel sprints from different projects that shares the same board but have nothing to do with each other.

On the Sprint Report and elsewhere on Jira, it shows the correct associated data. Just the Epic Burndown report that messes with the data, including the story points too on the Epic Report.

Workaround

Create another board specific to the projects that the Epic will be working on.