Store view switcher isn't working properly

I wish to present my store in 2 languages. But the store switcher in the front-end doesn't work properly. I selected it to be dropdown. As soon as I switched from one language to another the dropdown doesn't open anymore... even though the correct css class (.open) gets triggered on a click on the dropdown and the argument (expanded=true) also gets triggered.

I would be very thankful for anything helpful