I upgraded to version 13, and loaded the exact same iwzip project file that was generated by v12, and while most of it looks the same, I noticed one difference:

version 12:  http://www.iucrr.org/faq.html

version 13:  http://www.iucrr.org/test13/faq.html

(Refer to the attachment for numbered points, shown with square brackets.)

On version 12, the submenu [1] appears where it is supposed to, to the right of the main menu.

On version 13, the submenu [2] appears far to the left, butt up against the left margin, and not where it should be [3].

In the project, this page has two objects, one on top of the other.  The top object is a text object, the bottom object is an HTML object.  This page, and the codes I'm using, has worked for several versions prior to 13, but not in v13.

I've checked it with both Chrome and IE on two different PCs, one Win7 the other Win10.

Also, it's interesting to note the additional space added [4] above the text object.

I think it's a bug in v13.