Found an issue where I am unable to add a proxy server to the advanced network options.
If I tap the proxy server and then tap manual, the option to save or cancel disappear. The only way to exit that page is then to tap the back button which does not save any of the details.
To recreate, do the following
Settings
WiFi
Tap network name
Pencil icon to edit
Advanced options (cancel | save shows at the bottom of screen)
Proxy - tap down arrow and select manual
Cancel | Save now disappear from the bottom of screen