Turning cellular data off solves the issue for me. I also have personal hotspot off. It's worth understanding that word-processing programs on computers (and, evidently, on phones as well) start to "act up" and lose memory when a document is too long. One must break it up into several different documents. If your note becomes overlong, end it and begin a new note, 'part two' of the same title. And parts three, four and so on, if you are writing something that is thousands of words long. As a novelist, I have pages and pages of "notes" for whatever book I am writing, and for other books I may be outlining. I add to these notes and modify them all the time, so each Note is very lengthy. I now divide each one into several different "Notes" documents, labeled with the title and I, II,III,IV and so on. And by the way, it's clear by now that no one at Apple reads this. They are very helpful if you call their technical support, however. I have called them for computer issues several times. Not for the iPhone as yet, but we'll see..........