Unable to change the language for administrative access banner

Summary

The yellow admin banner remains in a specific language no matter what the language settings are in the General Configuration, the browser and the user profile.

Environment

Confluence 6.3.1

Steps to Reproduce

1. Set browser language to German from another language
2. Access the Confluence Admin console
3. The yellow banner at the top will stay in English (screen shots attached)

Expected Results

Everything on the instance would be in German.

Actual Results

The banner is in English.

Notes

Tried on two support engineer test instances. Please see screen shots for profile, global and browser language settings.

Workaround

Some customers have had the banner appear in the correct language after restarting Confluence:
https://community.atlassian.com/t5/Confluence-questions/Yellow-Administration-Banner-in-Confluence-Language-is-not/qaq-p/615318

There seems to be something that doesn't refresh the Confluence language, even when logging out or clearing the browser cookies. It seems that the banner language is set by the first language that it sees and sticks to that language regardless of the header

Accept-Language:en-AU,en;q=0.9,ja;q=0.8