I am writing an English article and have English UK selected as language in the new drop down box in the documents settings dialog. However, Juris-M frequently switches back to the system language, updating all citations to be not in English. I am not sure what triggers it, but I guess one of the triggers is inserting new citations.
The only way to bring back English citatations again is to open and close the settings dialog again (its not necessary to change anything, just pressing OK does the trick).

The refresh button does not change anything: When citations are in English, they stay English, when citations are in the system language (and should not be), they stay in the system language.