Pro Designer X 18: Bug with Exporting to SVG

I am creating icon-graphics for buttons used for a application toolbar to be used in Windows and MacOS; SVG for Windows and PDF for MacOS.

I have been making these graphics for the last few years and have never had this issue before.
As shown below the SVG export is missing information. The same Xara file produces a PDF perfectly.

Attachment 129690

Attached is the problem Xara file.
If the Layers Gallery is opened you will see that the "Layout" objects contained within 3 sub-groups.
If those subgroups are UNGROUPED then the SVG exports correctly.

Attachment 129684
Attachment 129685
Attachment 129686
Attachment 129689

Confirmed Xara Pro+ v21.2 has the same Parser but v18.0 fails with:

<?xml version="1.0" standalone="no"?>
<!DOCTYPE svg PUBLIC "-//W3C//DTD SVG 1.1//EN" "http://www.w3.org/Graphics/SVG/1.1/DTD/svg11.dtd">
XML Parsing error - line2, pos 11:
DTD is prohibited.
<!--Generator: Xara Designer (www.xara.com), SVG filter version: 6.6.0.1-->

@Xara - get Magix to fix this in the next 9 days or my Update Service will have expired and I'll be stuck with a buggy v18.0! [Sorry - my sarcasm filter is also buggy]

Acorn

I also noticed that in Windows Explorer that the thumbnail is displayed wrong,
but if I double-click on the thumbnail then in what I think is the Window's native viewer, it is displayed correctly.

Attachment 129691

The SVG's open perfectly in Inkscape, Firefox and Edge. (which could be the default viewer) Could it be that Chrome is the problem?

Opens fine in Chrome as well.

The toobar developer who used the problematic SVG file noticed the same issues.
When I ungrouped the sublevel grouping and then exported the SVG the problem was resolved.