How to reproduce it :

• in a content, create a table,
• insert text in a table cell > a p tag is created to wrap this text
• delete all content of this table cell > the p tag has disappeared
• add again a text into this same table cell > sometimes, the new p tag is not created

That is a problem when font size is declared with relative value. when the <p> is missing, the font size is not applied whereas it is applied on the text that is on other table cells.