Jira Gadgets on Confluence will show _MSG_gadget messages instead of some fields

Issue Summary

When adding Jira 8.0 gadgets to Confluence, random fields in gadgets will display as _MSG_gadget instead of the actual fields. At the same time, actual gadget titles will remain correct in the macro browser, the issue is observed in preview and on the pages.
On Jira side, gadgets will remain functional

Environment

• Jira 8.0
• Confluence 6.14.1

Steps to Reproduce

1. Connect Confluence 6.14.1 to Jira 8.0
2. Add Jira gadget feed
3. Add Some Jira Gadgets to a confluence page, for example, Issue Statistics

Expected Results

• Gadget is added and correctly populated in Confluence

Actual Results

• Gadget preview is showing bellow in the title, in both preview and on the page.

  __MSG_gadget.stats.statistics__: PROJ (Assignee)
  

Notes

Same is observed if the gadget is added directly or via gadget feed
Almost all gadgets are affected
The issue is observed regardless if Jira or Confluence are behind a proxy
Gadget titles will remain correct, if your gadget titles are showing wrong, please refer to How to fix gadget titles showing as __MSG_gadget KB.

Workaround

Currently, there is no known workaround for this behavior. A workaround will be added here when available