Current Issue : 

Unable to complete the sprint as a few issues (SubTask) are at won't fix state.

 Unable to complete the sprint after adding won't fix status.

Suggested Solution

Move the wont fix issue out of sprint or set the status to done.

Problem Definition

It is possible to close a parent issue (set to done) with open sub-tasks. When a user attempts to close a Sprint with these issues, a generic error occurs:

Sprint cannot be completed as there are incomplete subtasks on the following issues:

Suggested Solution

If there is a closed parent issue with open sub-tasks, it should give the user the option to either move all sub-tasks to done, or re-open the parent issue.

Workaround

Re-open the parent issue or close the sub-tasks using Bulk Change operations