That's not the problem, the thing is the editor used to do this when applying a class:

 

    </tr>  

 

and now does this:

 

<tr>
        <td><span class="some_class">some text</span></td>
        <td><span class="some_class">some text</span></td>
        <td><span class="some_class">some text</span></td>
        <td><span class="some_class">some text</span></td>
    </tr>

 

My class is defined to have a background color, so being in the  span now the backgroung has only the width of the text and not the width of the cell as intended.