It may be iOS 13 not your phone(s). I have issues with my 11 on Verizon. Happens when I connect to CarPlay, I will lose VoLTE and calls will revert to 1X, Siri won’t work, iMessages won’t go through. Google maps borks out. I need to restart the phone and then it goes back to normal. This happened on the Pro I had as well.
Browsing the MR iOS forum there appear to be a lot of bugs in iOS 13 so just be patient and hope Apple will address them? For $1000, shouldn’t be major bugs, but is what it is for now.