Skin changes lost after a reboot

I would also propose as a workaround, once the configuration is done, make the file immutable.
~# sudo chattr +i guisettings.xml

That would prevent any program from changing it again.
I’ll try it on my PI B+.
The Vero devices I have seem not to be affected.

PS: You can remove the immutable flag with:
~# sudo chattr -i guisettings.xml

Note the + vs. - sign.