This has happened several times over the last couple of days - over both vomments and PMs I'm writing - and isn't amenable to the "fix" I described above. In the PM mode, I find I have to "copy" everything I wrote and start over -- e.g., close and open the page again until it doesn't happen, then paste what I wrote before. Fortunately everything hidden copies. But this is a very long remedy.

********************
After a tardy proof read, I was going to edit "vomments". But maybe I've coined an apt word......