Strange behavior with vega embed/ vega lite locale

I observe a strange behavior I don’t understand: Following up upon: changing the locale for vega lite I changed my vega lite visualization to show the axes formated with German locale. (See Januar/ Februar,… x axes in

It worked and I kept the code untouched for a month. However, some weeks ago, - for one day - the visualization showed the axes with the default US locale ("January, February,…) Then without changing the code, it went back to the German locale. Today, I called the site and again had the US locale formatting now soem hours later, it shows in German again.

What is the reason for this when I didn’t ever change the code?
Are the imported libraries constantly changing and causing this effect ?