Drag/drop issues in a Sprint (planning mode) would cause the issue to go back to Backlog

Issue Summary

When dragging/dropping issues in a Sprint, it will initiate 2 AJAX requests (noticeable in instance with performance problem). In between the requests (after the 1st request but before the 2nd request), it is possible to drag/drop other issues. Once the 2nd request is made, it will cause the issue to be moved to the Backlog.

Steps to Reproduce

The Bug is heavily dependent on the instance's performance

1. Have a Backlog with over 1000 issues, create a Sprint
   • To increase the probability, expand the backlog to show all the issues
2. Drag/drop any issues in the Sprint
   • This will initiate the 2 AJAX requests (the screen will be greyed out twice)
3. In between the 2 AJAX requests, drag/drop some other issue in the Sprint
   • You will notice that the dragged issue will appear to have a duplicate:
     
4. Once the 2nd AJAX request occurs, the dragged issue will be moved to the backlog

Expected Results

Issues would be moved in the Sprint and not moved out to the Backlog

Actual Results

The issue will be moved out to the Backlog

Suggested solution:

There should be a lock between the 2 AJAX requests, hence users would not be able to drag/drop issues.

Workaround

None