Newsletter editor randomly saving/not saving changes

Last night I went to set up a newsletter to send. I copied from the last sent newsletter as I always do. When I went to edit the subject line, it would not save. No matter what I did, it would not save. I disabled various plugins I wasn’t really using. No change.

I then created a whole new newsletter from scratch. I was able to put in the proper subject line. I saved it. The save held. Then I added the standard header, saved it, and the header disappeared. I re-entered it, hit the “Next” button, went back to edit, and it was gone. I repeated several variations of this, it never saved.

I entered the body of the message and saved it. It held. I still could not add the Header info to the message in the Newsletter block editor. I tried entering the Header text directly into the Message body, and sometimes it saved, other times nothing.

My conclusion is that this program is randomly deciding when and what to save after each edit. To say that this is serious is beyond obvious. I cannot seem to perform any sequence of events to get changes to stay intact. This has never happened before with this plugin.

What do I do?