Hi!
I have a question, do you still use VirtualBox for the VM-s?
Yes, in my TODO list I have: stop using Vbox, maybe KVM? 
If it is so, maybe you could have a look at this thread:
*** TRYING TO INSTALL GUIXSD v0.15.0 FOR DAYS ***
they are experiencing the hang in the guile test suite on
VirtualBox.
Thanks, that would have been really helpful.  But I have been looking for it in the guix-devel archive and can't find it (used the expressions suggested)

Best regards,
g_bor

Regards!
Laura