Hello,
We've been checking the issue and it's a Google Doc problem. The problem is due to this element:
<w:gridCol/>
Google doesn't allow to set an empty w:gridCol property, but as you can read in the standard:
http://www.schemacentral.com/sc/ooxml/e-w_gridCol-1.html
w:gridCol is not mandatory but optional. So as PHPDocX follows the standard as much as possible, we'll don't force a value for this element. We recommend you to contact Google to fix it.
Regards.