iOS 12.1.2 may brick cellular connections and a hotfix didn’t help

In a rush to push out iOS 12.1.2 last week to potentially beat out an iPhone sales ban in China, it looks like Apple may have tripped over itself.
AppleInsider reported on Thursday, for whatever reason, the company has opted to re-roll the iOS 12.1.2 release just for the iPhone. The build number was changed from 16C101 on Monday to 16C104 on Thursday. It’s not immediately clear what tweaks Apple made and why.
Regardless of that, Forbes contributor Gordon Kelly has pointed out dozens of complaints on Twitter about the update bricking users’ cellular access on their iPhones.
@AppleSupport Hi, Is there any fix available for the network connectivity issue I am experiencing on my iPhone since updating to the latest iOS 12.1.2? #Applesupport #iOS12
— Harry Minhas (@harrym20) December 20, 2018
My phone won’t connect to cellular network at all after update to 12.1.2
— Chris PlayIt Payseur (@cPlayIt) December 21, 2018
While most of the complaints stem from after Thursday — which correlates with the 16C104 update — there was at least one tweet dating back to Wednesday, indicating that Apple might have tried to tackle the issue.
@AppleSupport I updated to ios 12.1.2 and now I cant call or text / receive calls or texts, what do I do?????!!!?!?!?!????!???,?? pic.twitter.com/qjUIqMQors
— han cman (@oddhannah) December 20, 2018
We checked on the Apple Support Communities and found only one thread on that issue and a scarce few others on other problems like camera malfunctions. That said, the top suggestion on our search for iOS 12.1.2 issues was a thread on “how to downgrade.”