Ordering by RANK and grouping by Epic does not work

[Thor Jacobsen]

When grouping by epic, and using ORDER BY Rank in the JQL, the issues are ordered by the rank of the epic, rather than the actual tasks in the JQL result.

This is without epic grouping:

This is with epic grouping:

See, that CS-18774 is top priority in the JQL response, but when grouping is applied it goes to the bottom.

I assume this is because the epic is ranked lower somewhere, but I assume this JQL response should reflect the rank of the result issues, and not the rank of the epics.