1) In Firefox,
2) select a style (Heading1, Heading2, etc.) for a line of text.

3) Position the cursor within the text and hit Enter.
4) In some cases (but not all), this causes the Style to reset to the default ""Paragraph"" style.  If the problem does not occur, try switching to HTML (or Preview) and back. Repeat the test again. The error should now occur."

 

Thanks