Wrong culture format displaying after publishing

[memergo]

Hi all, I have a strange situation with months being displayed in a seemingly random culture format. 

The issue is with formatted dates created with a calculated table (note Month has an "en-EN" culture arguement):

In Power BI Desktop the formatted month values look fine:

However, after my publishing it looks like this:

Google tells me this is Afar language, which I guess will be culture settings "aa", but I haven't the slightest clue why it does this.

So far I've checked:

• My machine Region is set to English (United States) format
• Regional settings in Power BI desktop are all fine:
  • Global Regional Settings: Application language is set to 'Use Windows default display language' 
  • Model language to 'Use application language'
  • Regional settings of the current file locale is set to English (United States)
• Our tenant is registered in West-Europe and the display language in my preferences is set to English (United States).
• The Semantic Model in the service has both Culture and Source Query Culture set to en-US as well when I inspect using Tabular Editor.

Does anyone have an idea what is going on?

[memergo · Accepted solution]

As a last ditch effort I tried removing the "en-EN" from the FORMAT() DAX functions and this ended up displaying the months correctly after publishing. Still don't understand why but at least my report makes sense now.