I've also just noticed that I can simply swipe down from the top and after dismissing from the status bar, the NavigationView appears as it does in the second pic (normal). This is very bizarre.

Updated.

I appreciate your help. Sorry about the errors, I didn't provide enough context code-wise, but I've just published my code to a public Github repo. Feel free to clone and investigate: https://github.com/cperault/fruitpedia