Communications breakdown error is shown when using Firefox

Summary

While editing issues or adding a comment, JIRA crashes with message: "communications breakdown".

Environment

• JIRA v1000.5.2
• This issue was reproduced on Firefox 46.0.1

Steps to Reproduce

1. Open JIRA Cloud on Firefox
2. Open an issue
3. Start editing 'Description'
4. Click on the project name

error-firefox.mp4

Expected Results

The description/comment should be saved and no error should be shown

Actual Results

Most of the times the description/comment are lost and the error is shown

Notes

Workaround

Use Chrome or Edge