An account complains about iPhone not accepting SIM after upgrading to iOS 12.1.4.
A series of faulty iPhones do not accept SIM, cannot connect to Wi-Fi, data after upgrading to iOS 12.1.4 Picture 2
A series of faulty iPhones do not accept SIM, cannot connect to Wi-Fi, data after upgrading to iOS 12.1.4 Picture 3
Another account says your iPhone cannot connect to wifi.Or even, there are faulty users who cannot use both data and Wifi.
A series of faulty iPhones do not accept SIM, cannot connect to Wi-Fi, data after upgrading to iOS 12.1.4 Picture 4
Notice of smartphone cannot receive sim.
Apple's @AppleSupport account gave feedback under a few tweets, but most were directed to its support page, not giving a specific fix.
Hopefully, Apple will really fix these serious bugs in the next update, and of course not adding new bugs.