I’m having the same text problems grrrrrrrr.
I did a few things.
I deleted FCPX and downloaded it again. That seem to stop the problem so fare (have only tested it for a few hours).
Also I have created a new user account but have not tested it yet, but I think that would work too.
The problem started yesterday while I was doing some title work on a movie. The thing got stock and I had to force quite. From that point on no new text is saved after quiting.
This is a huge issue since I’m doing lots if subtitles 🙁
-Kim