I'm using an S8+ and recently we got a "security update". Before this update, I was able to go into my wifi settings > advance > set proxy to manual and add IP address plus port.
Now every-time I do this, my phone fails to change the settings. It is almost like the "save" button is not working. As soon as I leave the page, my proxy settings get reset to "none".
I saw a post about possible apps that could mess with it, but I haven't installed any new apps or updated old ones. This issue started right after the latest update.