That's not the problem, the thing is the editor used to do this when applying a class:
<tr>
<td class="some_class">some text</td>
<td class="some_class">some text</td>
<td class="some_class">some text</td>
<td class="some_class">some text</td>
</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.