Broken Data Encryption 

Discovered by the popular Proton VPN service, Apple iOS 13.4 includes a security flaw that prevents the securement of your data while using a VPN on your iPhone. Proton states that when the VPN is enabled, iOS 13.4 will not shut out existing unsecured connections and “some are long-lasting and will stay open outside the VPN tunnel for minutes to hours. 

Some people reported a problem with downloading and installing the new update, particularly in the new iPhone 11, which can be solved most often with a hard reset.  Scattered reports about device lag, native and third party app issues, AirPlay issues, Touch ID and Face ID issues, and battery drain, as well as lock-ups, freezes, and crashes in Exchange, HomePod, iMessage, Wi-Fi, Bluetooth, and CarPlay have also been registered. 

Mobile Data Service Also Disabled in iOS 13.4

Various users have confirmed that they have lost mobile cellular coverage with the installation of iOS 13.3, and some also claim loss of Wi-Fi and cannot make phone calls or send regular text messages. 

iOS 13 4 Causes These Annoying iPhone Bugs - 5