Not sure if this is a bug
On mobile, after the drop down icon is clicked and the roll down page appeared. And when a selection is made, although the page is loaded, the roll down page persisted.
This is actually the intended behaviour of Bootstrap. We may be able to alter the behaviour, but for now, this is how it behaves.
I've been meaning to change how that works, I'll post an issue on github Thanks @quahfamili