This was caused by an issue with the February 2018 cumulative update - KB4077528 (OS Build 15063.936). The update was pulled after a few days and replaced with KB4092077 (OS Build 15063.936) on 8 March 2018 which fixed the issue.
The fix outlined the issue as follows:
Addresses issue where, after installing this update, some localized devices have incorrect strings or unusual behavior in different areas of the user interface (UI) that make the UI unusable.
You may have also noticed that the text strings in the Settings app are all wrong too!
The March 2018 cumulative update (KB4088782 (OS Build 15063.966)) was also released on 13 March and includes the fix as well.
Long story short, install the latest update and it'll fix the issue. If installing the latest update isn't an option for you at this time, then you can change the language settings to English US in Settings > Time & Language > Region & Language > Add a Language and it'll also fix the issue.