Hi Andre,
I've taken a look at the icons and have found a few "problems". "Problems" is in quotes because I am sure that they aren't true problems from Inkscape's perspective but they are for the easy extraction of the icons to individual files (which I'll need to add them to my book when they become the default).
The following icons have objects that are not included in the icon's group:
object_align inset_path dynamic_offset linked_offset draw_text
The easiest way (I think) of fixing this is to make a new group with the icon and the missing parts, ungroup the old icon group, and then rename the new group with the icon name.
Note that group g13443 is empty
Also, of probably little real significance, is that many of the objects are almost but not quite aligned with the grid. If you keep the XML editor window open you can see when you are just a fraction off.
Tav