It seems I found the issue.
If I clear the fields (subject and body) and save, it saves!
If I set the subject to a single string value, like "abc", and the body to nothing and save, it saves!
If I set the subject to a single string value, like "abc", and the body to "abc" and save, it saves!
If I set the subject to a single string value, like "abc", and the body to "<p>abc</p>" and save, it saves!
If I set the subject to a single string value, like "abc", and the body to "<p>abc</p><p>abc</p>" and save, it dose NOT save!
So it seems that my html code, which contains tables, paragraphs, etc, is not being saved for possibly the same reason the last test above didn't.
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