After disconnecting from wifi the phone won't reconnect to 4G again. It doesn't matter if it disconnects from wifi because of bad signal or turning wifi off on the phone.
To reconnect to 4G I need to restart the phone or cycle airplane mode.
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer?