Using Custom Cultures in Chrome now fails in Power BI Embedded

In our application users can use custom cultures, e.g. en-FR, en-ET, en-PL etc. and can view embedded Power BI Reports.

We set the config > localeSettings > Langauge and FormatLocale using these custom cultures.

This has all been working well until the last couple days when it fails in Chrome, Safari and other WebKit/Blink derived-browsers etc.

Developer tools shows it goes:

• reportEmbed?reportid=xxxxxxxx&etc
• globalize.culture.en-FR.js (which does not exist). This issues a 302 redirect to
• ErrorPage?code=404 (this issues a 200 OK response, and not a 404 or an error code)
• reportEmbed?reportid=xxxxxxxx&etc

And just gets stuck in a loop going round and round in circles, increasing CPU usage and firing up the computer's fans until the browser hangs.

Firefox does not suffer from this problem, it still sees the 302 on the globalize culture file, and the redirect to the ErrorPage, which still issues a 200 OK response, but it displays the data in a browser default language.

This issue only started to exhibit itself in the last couple of days. Prior to that, the Chrome/Safari browsers worked like Firefox.