Sprint Health gadget does not record scope change reliably

Summary

The Sprint Health gadget does sometimes record scope change correctly but sometimes not. 

Steps to Reproduce

Working case : 

1. Create a board from a project (example query : project = PQR AND issuetype = Story ORDER BY Rank ASC)
2. Create a Sprint (Example "Sprint 1")
3. Add (estimated)issues to the sprint
4. Start Sprint
5. Add the Sprint Health gadget to the dashboard. See the Sprint Scope change is reported as 0%
6. Add more (estimated)issues to the Sprint while it is running
7. Refresh the dashboard Sprint health gadget.
8. Notice it shows scope change 

Non working case : 

1. Create another board from same project (example query : project = PQR AND issuetype = Bug ORDER BY Rank ASC)
2. Right click on issues in the backlog and edit the issues to add the same Sprint from previous board "Sprint 1"
3. Now issues from the second board are added to the common Sprint from both boards
4. Add another Sprint Health gadget to the dashboard based on this board and the common Sprint
5. Notice that the Scope change is always zero.
6. Add more (estimated)issues to the Sprint
7. The dashboard gadget always shows scope change as zero.

Workaround

There is currently no workaround.