I had a problem. Since 10.3 I couldn't send a text picture. I get an error something like "Can't send message because message app isn't active" or some such. After a few hours, it fixed itself. But seems to be chewing up my battery.
It seems the update, despite their claims, was to stop a phony ransomware from propagating.
I think I'll cycle power now. Let's see, where do I unplug it....